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Three years after the Tea Party burst onto the national scene with its anti-tax message, the diverse movement is trying to remain a political force and shape elections – amid recent polling that shows shifting American attitudes.

If the Republican primary battle is any gauge, the Tea Party on the ground level is flexing its influence. Tea Party-aligned voters have picked the GOP winner this year in 17 of 18 presidential primary contests, in races for which exit polling information was available.

Yet on the third anniversary of the movement's kick-off Tax Day rallies, questions about the Tea Party’s future and strength remain. The movement -- which includes thousands of small, independent groups across the country and claims no allegiance to national political parties -- was a major factor in the 2010 elections. With the help of many Tea Party-backed, first-time candidates, Republicans took back the House in the landslide election.

However, a recent Washington Post-ABC News poll showed interest in the movement may be waning.

The poll found 41 percent of Americans now say they support the Tea Party movement, compared to 47 percent in September. It also found six in 10 Americans have no real interest in additional information about the movement, and 41 percent aren’t interested "at all.”

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In addition, 39 percent have at least some interest, but just 9 percent are very interested. Among those with interest, roughly six in 10 already support the movement, according to the April 5-8 poll of 1,103 adults.

The Tea Party’s biggest groups have tried this election season to recapture the enthusiasm and interest from the midterms, holding rallies, bus tours and even sponsoring GOP presidential debates. Yet they acknowledge that 2012 is not the same political environment as the one in which the movement started.

“This is completely different than 2009,” said Sal Russo, co-founder and  chief strategist of Tea Party Express, which in September co-sponsored in GOP debate in Tampa, Fla. “People were frantic. They were grabbing us by the lapels and asking ‘what do we do.’ Now there’s less need for sign waving.”

Still, the group is firing up the bus again with an 11-day, cross-country "Restoring the American Dream" tour that begins April 27.

Russo argued the recent poll indicates what Tea Party organizers already know -- that roughly 85 percent of those who originally joined had never been politically active, so there is now a smaller pool of the uninitiated. And he said the movement has a basic, unchanged message on which most Americans already agree -- reduce the federal debt and reduce the size and cost of government.

The Tea Party Express has not endorsed presumptive GOP nominee Mitt Romney, and Russo gave no indication Tuesday of his group’s immediate intention to do so. However, the group has backed five Senate candidates, including Richard Mourdock, a Republican Indiana state treasurer challenging long-time incumbent Sen. Dick Luger in the party primary.

In the presidential primaries, Tea Party voters were by no means unanimous in their choice. Exit polls show they picked a range of candidates depending on the state -- from Rick Santorum in his kickoff victory in Iowa to Newt Gingrich in Georgia and South Carolina to Romney in Wisconsin.

The massive Tea Party Patriots also co-sponsored a presidential debate in the GOP primary season, looking to make its mark on the closely watched race. That decision, though, led to tension within the national network and eventually resulted in co-founder Mark Meckler resigning from Tea Party Patriots. Meckler reportedly was concerned that by co-sponsoring a debate, the Tea Party was compromising its independence.

Fellow co-founder Jenny Beth Martin later defended the group, saying it continues to be "transpartisan" and holds both parties accountable.