RUTLAND, Vt. — In the four years after the financial crisis struck, a great wave of federal stimulus money washed over Rutland County. It helped pay for bridges, roads, preschool programs, a community health center, buses and fire trucks, water mains and tanks, even a project to make sure fish could still swim down the river while a bridge was being rebuilt.

Just down Route 4, at the New York border, the landscape abruptly turns from spiffy to scruffy. Washington County, N.Y., which is home to about 60,000 people — just as Rutland is — saw only a quarter as much money.

“We didn’t receive a lot,” said Peter Aust, the president of the local chamber of commerce on the New York side. “We never saw any of the positive impact of the stimulus funds.”

Vermont’s 625,000 residents have two United States senators, and so do New York’s 19 million. That means that a Vermonter has 30 times the voting power in the Senate of a New Yorker just over the state line — the biggest inequality between two adjacent states. The nation’s largest gap, between Wyoming and California, is more than double that.

The difference in the fortunes of Rutland and Washington Counties reflects the growing disparity in their citizens’ voting power, and it is not an anomaly. The Constitution has always given residents of states with small populations a lift, but the size and importance of the gap has grown markedly in recent decades, in ways the framers probably never anticipated. It affects the political dynamic of issues as varied as gun control, immigration and campaign finance.

In response, lawmakers, lawyers and watchdog groups have begun pushing for change. A lawsuit to curb the small-state advantage in the Senate’s rules is moving through the courts. The Senate has already made modest changes to rules concerning the filibuster, which has particularly benefited senators from small states. And eight states and the District of Columbia have endorsed a proposal to reduce the chances that the small-state advantage in the Electoral College will allow a loser of the popular vote to win the presidency.

To be sure, some scholars and members of Congress view the small-state advantage as a vital part of the constitutional structure and say the growth of that advantage is no cause for worry. Others say it is an authentic but insoluble problem.

What is certain is that the power of the smaller states is large and growing. Political scientists call it a striking exception to the democratic principle of “one person, one vote.” Indeed, they say, the Senate may be the least democratic legislative chamber in any developed nation.

Behind the growth of the advantage is an increase in population gap between large and small states, with large states adding many more people than small ones in the last half-century. There is a widening demographic split, too, with the larger states becoming more urban and liberal, and the smaller ones remaining rural and conservative, which lends a new significance to the disparity in their political power.

The threat of the filibuster in the Senate, which has become far more common than in past decades, plays a role, too. Research by two political scientists, Lauren C. Bell and L. Marvin Overby, has found that small-state senators, often in leadership positions, have amplified their power by using the filibuster more often than their large-state counterparts.

Beyond influencing government spending, these shifts generally benefit conservative causes and hurt liberal ones. When small states block or shape legislation backed by senators representing a majority of Americans, most of the senators on the winning side tend to be Republicans, because Republicans disproportionately live in small states and Democrats, especially African-Americans and Latinos, are more likely to live in large states like California, New York, Florida and Illinois. Among the nation’s five smallest states, only Vermont tilts liberal, while Alaska, Wyoming and the Dakotas have each voted Republican in every presidential election since 1968.

Recent bills to overhaul the immigration system and increase disclosure of campaign spending have won the support of senators representing a majority of the population but have not yet passed. A sweeping climate bill, meant to raise the cost of carbon emissions, passed the House, where seats are allocated by population, but not the Senate.

Each of those bills is a major Democratic Party priority. Throughout his second term, President Obama is likely to be lining up with a majority of large-state Congress members on his biggest goals and against a majority of small-state lawmakers.

It is easiest to measure the small-state advantage in dollars. Over the past few years, as the federal government has spent hundreds of billions to respond to the financial crisis, it has done much more to assist the residents of small states than large ones. The top five per capita recipients of federal stimulus grants were states so small that they have only a single House member.

“From highway bills to homeland security,” said Sarah A. Binder, a political scientist at George Washington University, “small states make out like bandits.”

Here in Rutland, the federal government has spent $2,500 per person since early 2009, compared with $600 per person across the state border in Washington County.

As the money started arriving, Senator Bernard Sanders, the Vermont independent, took credit for having delivered a “hefty share of the national funding.” Senator Kirsten Gillibrand, a New York Democrat, vowed to fight for her state’s “fair share.”

As a matter of constitutional design, small states have punched above their weight politically for as long as the United States has existed. The founding of the country depended in part on the Great Compromise, which created a legislative chamber — the Senate — in which every state had the same political voice, regardless of population. The advantage small states enjoy in the Senate is echoed in the Electoral College, where each state is allocated votes not only for its House members (reflecting the state’s population) but also for its senators (a two-vote bonus).

No one expects the small-state advantage to disappear, given its constitutional roots. But its growing importance has caused some large-state policy makers and advocates for giving all citizens an equal voice in democracy to begin exploring ways to counteract it. Those pushing for change tend to be Democrats.

One plan, enacted into law by eight states and the District of Columbia, would effectively cancel the small states’ Electoral College edge. The nine jurisdictions have pledged to allocate their 132 electoral votes to the winner of the national popular vote — if they can persuade states with 138 more votes to make the same commitment. (That would represent the bare majority of the 538 electoral votes needed for a presidential candidate to prevail.)

The states that have agreed to the arrangement range in size from Vermont to California, and they are dominated by Democrats. But support for changing the Electoral College cuts across party lines. In a recent Gallup Poll, 61 percent of Republicans, 63 percent of independents and 66 percent of Democrats said they favored abolishing the system and awarding the presidency to the winner of the popular vote.

In 2000, had electoral votes been allocated by population, without the two-vote bonuses, Al Gore would have prevailed over George W. Bush. Alexander Keyssar, a historian of democracy at Harvard, said he would not be surprised if another Republican candidate won the presidency while losing the popular vote in coming decades, given the structure of the Electoral College.

Critics of the outsize power of small states have also turned to the courts. In December, four House members and the advocacy group Common Cause filed an appeal in a lawsuit challenging the Senate’s filibuster rule on the ground that it “upsets the balance in the Great Compromise” that created the Senate.

The filibuster “has significantly increased the underrepresentation of people living in the most populous states,” the suit said. But for the rule, it said, the Dream Act, which would have given some immigrants who arrived illegally as children a path to legalization, and the Disclose Act, requiring greater reporting of political spending, would be law.

A federal judge in Washington dismissed the suit, saying he was “powerless to address” what he acknowledged was an “important and controversial issue.” The judge instead sided with lawyers for the Senate, who said that the challengers lacked standing to sue and that the courts lacked power to rule on the internal workings of another branch of the government.

However these individual efforts fare, the basic disparity between large and small states is wired into the constitutional framework. Some scholars say that this is as it should be and that the advantages enjoyed by small states are necessary to prevent them from becoming a voiceless minority.

“Without it, wealth and power would tend to flow to the prosperous coasts and cities and away from less-populated rural areas,” said Stephen Macedo, a political scientist at Princeton.

Gary L. Gregg II, a political scientist who holds the Mitch McConnell Chair in Leadership at the University of Louisville, similarly argued that urban areas already have enough power, as the home of most major government agencies, news media organizations, companies and universities. “A simple, direct democracy will centralize all power,” he wrote recently, “in urban areas to the detriment of the rest of the nation.”

Others say the country needs to make changes to preserve its democratic vitality. They have called for an overhaul of the Constitution, as far-fetched an idea as that may be.

“The Senate constitutes a threat to the vitality of the American political system in the 21st century,” said Sanford Levinson, a law professor at the University of Texas, “and it warrants a constitutional convention to rectify it.”

Frances E. Lee, a political scientist at the University of Maryland, said the problem was as real as the solution elusive, adding that she and other scholars have tried without success to find a contemporary reason to exempt the Senate from the usual rules of granting citizens an equal voice in their government. “I can’t think of any way to justify it based on democratic principles,” Professor Lee said.

Fresno, Calif., is a city of a half-million people with a long list of problems, including 14 percent unemployment, the aftermath of a foreclosure crisis, homeless encampments that dot the sun-blasted landscape and worries about the safety of the surrounding county’s drinking water.

A thousand miles away, a roughly comparable number of people inhabit the entire state of Wyoming. Like Fresno and its environs, Wyoming is rural, with an economy largely based on agriculture. It is also in much better shape than Fresno, with an unemployment rate around 5 percent.

Even so, Wyoming receives far more assistance from the federal government than Fresno does. The half-million residents of Wyoming also have much more sway over federal policy than the half-million residents of Fresno. The vote people in Fresno remember best was taken in 2007, when an immigration overhaul bill that included a guest worker program failed in the Senate. Both agricultural businesses and leaders of Fresno’s large Hispanic population supported the bill, much as polls suggested a majority of Americans did.

But the immigration bill died in the Senate after a 53-46 vote rejecting a bid to move the bill forward to final passage. Wyoming’s two senators were in the majority and California’s two senators on the losing side.

Had the votes been allocated by population, the result would have been lopsided in the other direction, with 57 votes in favor and 43 against.

Even 57 votes would not have been enough to overcome a filibuster, which requires 60. In the last few years, 41 senators representing as little as a third of the nation’s population have frequently blocked legislation, as the filibuster (or the threat of it) has become a routine part of Senate business.

Beyond the filibuster, senators from Wyoming and other small states regularly oppose and often thwart programs popular in states with vastly bigger populations. The 38 million people who live in the nation’s 22 smallest states, including Wyoming, are represented by 44 senators. The 38 million residents of California are represented by two senators.

In one of every 10 especially consequential votes in the Senate over the two decades ending in 2010, as chosen by Congressional Quarterly, the winning side would have lost had voting been allocated by population. And in 24 of the 27 such votes, the majority of the senators on the winning side were Republicans.

David Mayhew, a political scientist at Yale, cautioned that the political benefit to Republicans is “quite small as well as quite stable,” adding that it is important not to lose sight of small blue states like Delaware, Hawaii, Rhode Island and Vermont. But he acknowledged that small states of both political stripes receive disproportionate federal benefits. Professor Lee, an author of “Sizing Up the Senate: The Unequal Consequences of Equal Representation,” argues that the partisan impact of the small-state advantage is larger. “There is a Republican tilt in the Senate,” she said.

“The way Republicans are distributed across the nation is more efficient,” she added, referring to the more even allocation of Republican voters, allowing them to form majorities in small-population states. Democrats are more tightly clustered, especially in large metropolitan areas.

Equal representation of the states in the Senate is a consequence of the Great Compromise, the 1787 deal that resolved a seemingly intractable dispute between the smaller states and a handful of large ones like Massachusetts, Pennsylvania and Virginia. But the country was very different then. The population was about four million, and the maximum disparity in voting power between states was perhaps 11 to 1. It is now six times greater than that. Even scholars who criticize how voting power is allocated in the Senate agree that parts of its design play an important role in the constitutional structure. With its longer terms and fewer members, the Senate can, in theory, be more collegial, take the long view and be insulated from passing passions.

But those qualities do not depend on unequal representation among people who live in different states. The current allocation of power in the Senate, many legal scholars and political scientists say, does not protect minorities with distinctive characteristics, much less disadvantaged ones.

To the contrary, the disproportionate voting power of small states is a sort of happenstance that has on occasion left a stain on the nation’s history.

Robert A. Dahl, the Yale political scientist, who is 97 and has been studying American government for more than 70 years, has argued that slavery survived thanks to the disproportionate influence of small-population Southern states. The House passed eight antislavery measures between 1800 and 1860; all died in the Senate. The civil rights movement of the mid-20th century, he added, was slowed by senators representing small-population states.

As the population of the United States has grown a hundredfold since the founding, to more than 310 million, the Supreme Court has swept away most instances of unequal representation beyond the Senate. In a series of seminal cases in the 1960s, the court forbade states to give small-population counties or districts a larger voice than ones with more people, in both state legislatures and the House.

“The conception of political equality from the Declaration of Independence, to Lincoln’s Gettysburg Address, to the Fifteenth, Seventeenth, and Nineteenth Amendments can mean only one thing — one person, one vote,” Justice William O. Douglas wrote for the court in 1963, referring to the amendments that extended the franchise to blacks and women and required the popular election of the Senate.

The rulings revolutionized American politics — everywhere but in the Senate, which the Constitution protected from change and where the disparities in voting power have instead become more extreme.

In his memoirs, Chief Justice Earl Warren described the cases from the 1960s establishing the equality of each citizen’s vote as the most important achievement of the court he led for 16 years. That made them more important in his view than Brown v. Board of Education, which ordered the desegregation of public schools, and Gideon v. Wainwright, which guaranteed lawyers for poor people accused of serious crimes.

“Legislators represent people, not trees or acres,” Chief Justice Warren wrote for the court in 1964, rejecting the argument that state senators, like federal ones, could represent geographic areas with varying populations. “Legislators are elected by voters, not farms or cities or economic interests.”

Applying that principle to the Senate would be very hard. Even an ordinary constitutional amendment would not do the trick, as the framers of the Constitution went out of their way to require states to agree before their power is diminished. Article V of the Constitution sets out the procedure for amendments and requires a two-thirds vote of both houses of Congress or action by two-thirds of state legislatures to get things started. But the article makes an exception for the Senate. “No state, without its consent, shall be deprived of its equal suffrage in the Senate,” the article concludes.

The United States Senate is hardly the only legislature that does not stick strictly to the principle of equal representation. Political scientists use the term “malapportioned” to describe the phenomenon, and it is common around the world.

But the Senate is in contention for the least democratic legislative chamber. In some other countries with federal systems, in which states or provinces have independent political power, a malapportioned upper house may have only a weak or advisory role. In the United States, the Senate is at least equal in power to the House, and it possesses some distinctive responsibilities, like treaty ratification and the approval of presidential appointments. A recent appeals court decision severely limiting the president’s power to make recess appointments, if it stands, will further increase the Senate’s power.

Professor Dahl has calculated the difference between the local government unit with the most voting power and that with the least. The smallest ratio, 1.5, was in Austria, while in Belgium, Spain, India, Germany, Australia and Canada the ratio was never higher than 21 to 1.

In this country, the ratio between Wyoming’s representation and California’s is 66 to 1. By that measure, Professor Dahl found, only Brazil, Argentina and Russia had less democratic chambers. A separate analysis, by David Samuels and Richard Snyder, similarly found that geographically large countries with federal systems tend to overrepresent sparsely populated areas.

This pattern has policy consequences, notably ones concerning the environment. “Nations with malapportioned political systems have lower gasoline taxes (and lower pump prices) than nations with more equitable representation of urban constituencies,” two political scientists, J. Lawrence Broz and Daniel Maliniak, wrote in a recent study. Such countries also took longer to ratify the Kyoto Protocol on climate change, if they ratified it at all. These differences were, they wrote, a consequence of the fact that “rural voters in industrialized countries rely more heavily on fossil fuels than urban voters.”

In 2009, the House of Representatives narrowly approved a bill to address climate change, but only after months of horse-trading that granted concessions and money to rural states. That was an example, Mr. Broz and Mr. Maliniak said, of compensating rural residents for the burdens of reducing greenhouse-gas emissions.

But it was not enough. The bill died in the Senate.