“For the third national election in a row, independent voters may be poised to vote out the party in power,” Pew concludes after its study of 2,816 registered voters, including 1,069 independent registered voters. The study, conducted Aug. 25 to Sept. 6, has a margin of error of 2.5 percentage points.

If the breadth of the GOP’s gains this fall is determined by these independent voters, the one possible problem for the party, the poll found, could be if GOP candidates pay too much attention to a handful of social issues that historically have driven away some swing voters.

That is among the few areas in which more independents, 39 percent, say Democrats reflect their views, compared with 33 percent who say Republicans do.

Republican strategists are mindful of the risk, which helps explain why House GOP leaders downplayed such issues as abortion and gay marriage when they unveiled “A Pledge to America,” a pamphlet that emphasized the economic agenda Republicans say they will push if they regain the majority.

It’s a message they hope will have broad appeal with independent voters who, the Pew survey found, are paying more attention to and are likely to participate in higher numbers in this year’s midterms than in those of the past decade.

Unlike the most recent election cycles, when independents complained about the lack of progress in Washington on major issues facing the country, these critical swing voters now are expressing high anxiety with what Congress and the White House have already done.

Overall, 45 percent of independents disapprove of the health care reforms passed this year, compared with 41 percent who approve of them. A third of independents say Obama’s economic policies have made conditions worse for them rather than better, compared with 24 percent who take a more positive view.

“They feel that the issues have been dealt with but not in a way that is satisfactory to them,” said Andrew Kohut, president of the Pew Research Center.

The upshot is that independents appear to be clamoring for a time-out in Washington, as they absorb what already has passed and stall any other big new reforms.

That sentiment is evident in the survey’s findings regarding their views toward Washington and the course of the country. In 2006, 53 percent of independents said they preferred a smaller government with fewer services; today, 59 percent want a check on government growth. In 2006, 67 percent of independents were not satisfied with national conditions; today, 76 percent aren’t happy.

A similar waning of the pro-government posture among independents can be found in the NBC News/Wall Street Journal polls, according to an analysis by Bill McInturff, the Republican analyst on the bipartisan team that conducts the survey.

“Trust in government is at one of the lowest points in 60 years of polling,” Kohut said. “It’s a backlash against what is seen as government policies and programs that are too liberal or too much in the vein of government expansion.”

About the only good news for Democrats in the survey is that a reasonable chunk — about 40 percent — of independents said they still maintain some level of support for the president or his party. Those respondents, however, are not nearly as motivated to vote as their discontented independent brethren.

The emotions driving the sharp shift among independents are slightly different than those behind the Republican-leaning tea party movement and other conservatives.

In the poll, a third of Republicans said they are “angry” at the federal government, compared with about a quarter of independents.

Still, one-half of the independents said they are frustrated with Washington and made clear they intend to do something about it.

More so than Democrats interviewed in the poll, independents say they are giving “a lot of thought” to the midterms, and they are about as likely as Democrats to say they will definitely vote. Roughly half of them, 49 percent, said they will back a Republican, while 43 percent said they’d support a Democrat.

Those figures are even more striking when only “likely voters” are taken into consideration.

In a string of polls from 2002 to 2009, voters generally preferred to see an expanded role for government in solving the nation’s problems. A year ago, when Congress was enmeshed in the health care debate, that trend shifted as more voters began registering concerns about the size and role of government.

The change of heart was especially true among independents. Last September, 56 percent said government was trying to do too many things, and the gap has only widened and now stands at double digits.

Among them, 49 percent said they will support a GOP candidate, compared with 36 percent who are likely to vote Democratic — and that “is a pivotal factor behind the Republican Party’s overall 7-point lead among all likely voters at this point in the campaign,” the Pew report notes.

On the issues, Republicans have overtaken Democratic advantages on managing foreign policy, national security and the economy.

However, the Democrats maintained an edge on social issues. For instance, more than twice as many independents as Republicans favor allowing same-sex marriages.

Social conservative groups have tried to elevate their issues, but Kohut said Republican leaders would be wise to resist them.

“Those were issues that were very successful in keeping the base together in the Bush years,” he said. “But you don’t need issues like that to keep the base together. The base is unified in its negative response to Obama and the economy.”