For some leaders in the tea party movement, the ongoing skirmish over whether presidential contender Mitt Romney should speak at a Tea Party Express rally in New Hampshire on Monday is anything but an internecine quarrel.

It is the opening shot, they say, in an all-out effort to make sure the former Massachusetts governor does not win the Republican nomination to challenge President Obama next year.

Whether they have the reach to win that battle is uncertain. Romney, despite his slip from front-runner status since Texas Gov. Rick Perry entered the GOP race, remains a formidable candidate with the most money and a deep organization and fundraising network. His weaknesses among conservatives — most notably his support for a health-care overhaul in Massachusetts that became the basis for Obama’s health-care plan — are somewhat offset by his business acumen and moderation on social issues by those most motivated by beating Obama.

That hasn’t stopped some tea party leaders from launching an anyone-but-Romney campaign that will include protesting during his appearances at conservative functions and working to counter his organization in crucial states, such as Florida and Ohio, that come after the earliest primaries next year.

The idea is to convince people that Romney is unacceptable, pointing to his health-care overhaul and what they see as his unconvincing record on spending and tax cuts while governor of Massachusetts. Another point of friction: Romney has done little outreach to local tea party groups, part of the reason for the protest in New Hampshire.

The risk, if they fail, is that they undermine the political influence that the movement has worked tirelessly for two years to build.

Matt Kibbe, president of the national organization FreedomWorks, said it’s a risk worth taking.

“I think the message from the tea party in New Hampshire is, ‘We’re not useful idiots,’ ” Kibbe said, repeating a phrase that has popped up increasingly in recent days to remind activists not to capitulate to the Republican establishment. “There’s this long tradition in the Republican Party to simply elect the next guy in line. That’s how we got John McCain, and that’s how we got Mitt Romney. If somebody says that early and often, you have a better potential to see if somebody can emerge as a true competitor to Romney.”

Kibbe said his organization does not prefer a specific candidate over Romney, but he said at least three — Perry, Rep. Michele Bachmann (Minn.) and Rep. Ron Paul (Tex.) — are the most appealing to donors and activists he speaks to each week.

Perhaps the biggest challenge for those who hope to block Romney is the fractured nature of the tea party itself. Many activists oppose, on principle, an effort led by a national group to tell them which candidates are acceptable and which aren’t.

“We want everyone to understand the positions of the candidates and to make their own decisions,” said Vicki Higbee, a member of the First Coast Tea Party in the Jacksonville, Fla., area. The group is compiling the records of each candidate and posting them on its Web site for members to use to make their own choices. First Coast also would gladly welcome Romney to speak if he wanted to, Higbee said. “We want to hear everyone. We want everyone to have the opportunity to make their own decision based on knowing all the facts.”

The other huge obstacle to knocking out Romney is his support among moderate and establishment Republicans who view him as the party’s best shot at defeating Obama. Kibbe rejects the electability argument, saying a Romney nomination would keep more unexcited conservatives home on Election Day than it would draw out crucial independents.

“Elections are won at the margins,” he said. “There will certainly be a lot of tea partyers who will hold their noses and vote for any Republican because Obama has been a disaster for the economy,” he said. “But we’re going to need every vote, every person willing to walk precincts, every bit of energy that we saw in 2010, if we’re going to beat Obama.”

A number of GOP operatives questioned that logic.

“I don’t think there’s any chance of that happening,” said Joe Gruters, chairman of the Sarasota County GOP in Florida. “President Obama has fired up so many people that it’s my belief that any of our candidates are going to win.”

Romney’s campaign declined to comment, but he appears all too aware of the threat to his campaign from the tea party — particularly since Perry, who is popular with the grass-roots movement, joined the race. In addition to teaming up with the Tea Party Express for the Manchester, N.H., rally, Romney also reversed an earlier decision and will attend a presidential forum in Columbia, S.C., with tea party favorite Sen. Jim DeMint (S.C.) on Monday afternoon.

“He’s going to take some heat, but there’s some potential upside on the trail where he can show he can take the hard criticism and hard contrast and see how he reacts,” said Rich Killion, a Republican operative in New Hampshire who most recently worked for Tim Pawlenty, the former Minnesota governor who dropped out of the race last month. “It’s going to be a very difficult task, but sometimes those are great opportunities.”

Nonetheless, even among tea partyers who would welcome Romney at political events, he is rarely the choice over Bachmann, Perry or Paul. And there is Romney’s slowness to solicit the views of local tea party activists, which some see as a slight.

“I haven’t had the chance to talk to him,” said Jerry DeLemus, chairman of the Granite State Liberty Patriots. “I’ve asked and asked and asked for the chance to talk to him, and I might as well be talking to a wall. If he wants to have that conversation, then he should reach out. But he hasn’t reached out.”