Leaders of more than 70 tea party groups in Indiana gathered last weekend to sign a proclamation saying they would all support one candidate — as yet undetermined — in a primary challenge to Sen. Richard G. Lugar, the Republican who has represented the state since 1977.

They are organizing early, they say, to prevent what happened last year, when several tea party candidates split the vote in Republican Senate primaries, allowing the most establishment of the candidates to win with less than 40 percent.

The meeting in Sharpsville was hardly the exception. Just three months after the midterm elections, tea party organizers are preparing to challenge some of the longest-serving Republican incumbents in 2012.

In Maine, there is already one candidate running on a tea party platform against Sen. Olympia J. Snowe. Supporters there are seeking others to run, declaring that they, too, will back the person they view as the strongest candidate to avoid splitting their vote. In Utah, the same people who ousted Sen. Robert F. Bennett at the state’s Republican convention last spring are now looking at a challenge to Sen. Orrin G. Hatch.

The early moves suggest that the pattern of the last elections, in which primaries were more fiercely contested than the general election in several states, may be repeated.

They also show how much the tea party has changed the definition of who qualifies as a conservative. While Snowe is widely considered a moderate Republican, Hatch is not. Lugar, similarly, defines himself as a conservative. He argues that he has consistently won praise from small-business groups, supported a balanced budget amendment and pushed for a reduction in farm subsidies and the closing of agricultural extension offices as part of an effort to reduce unnecessary spending — all initiatives that fall under the smaller government rubric of the tea party.

The advocates in Indiana, which national tea party groups say has the most organized of the primary efforts, point to Lugar’s push for the New START nuclear treaty, which the Senate approved in December; his sponsorship of the Dream Act, which would have granted a path to citizenship for limited groups of illegal immigrants; and his votes for President Barack Obama’s picks for the Supreme Court, Justices Sonia Sotomayor and Elena Kagan.

"The senator would call it bipartisanship, but we think you’re siding with the other side," said Greg Fettig, a tea party supporter in Indiana.

Another, Mark Holwager, said, "He may have been a conservative at one time, but he definitely leans to the left now."

The coalition of tea party groups, calling itself Hoosiers for a Conservative Senate, plans to hold a caucus in June where the 70-odd groups involved will choose a candidate to run against Lugar in the primary next May. In the meantime, the group has designated a coordinator for each of the state’s congressional districts to begin a campaign to educate voters about what tea party supporters call Lugar’s liberal record.

The group has also had discussions with several national groups that played a role in primaries last year where establishment candidates or Republican incumbents lost to tea party challenges, including FreedomWorks, the Tea Party Express and the Club for Growth.

Those behind tea party challenges say they learned their lesson about splitting the vote from several primary contests last year, including the Senate races in Illinois and Indiana and congressional races in Virginia, where a flood of tea party candidates resulted in a moderate or establishment candidate winning.

But so far there are few declared candidates. In Utah, some tea party supporters say they would back a run by Rep. Jason Chaffetz, who won his congressional seat in 2008 after challenging an incumbent Republican, Chris Cannon, in the primary. That race became a kind of trial run for tea party primaries, with many of the same people who worked on Chaffetz’s campaign working to unseat Bennett last year.

Still, there is some division. The Tea Party Express, a national group started by longtime Republican consultants, recently announced that it would not back a challenge to Hatch, calling him "as good as it gets" for Republicans. The Club for Growth, which has poured money into other Republican primary challenges, issued a statement disagreeing.

Utah is a reliably Republican state, so whoever wins the primary is almost assured to win the general election.

In Maine, even some tea party supporters say the challenge is trickier: voters have long preferred moderates and independents. Still, some note the success of the state’s new Republican governor, Paul LePage, who was elected with tea party support and is winning applause for pushing to cut the budget.

"The way the state’s been turning, I think if we got a decent conservative in there, it wouldn’t be that much of a problem to win," said Pete Harring, a tea party supporter in Maine. "People are starting to realize we’re just too deep in a hole; we have to do something."

LePage narrowly beat an independent candidate in a five-way general election, winning less than 40 percent of the vote. With that in mind, tea party supporters have also discussed running a third-party candidate.

In Indiana, several tea party supporters met with Lugar last month, and he argued his conservative credentials. Unconvinced, they announced that they would pursue a primary challenge, and that the first step would be to unify behind one Republican. Potential candidates include a state senator, Mike Delph, and the state treasurer, Richard E. Mourdock.