With the official formation of a congressional Tea Party Caucus, Rep. Michele Bachmann has thrust an existential question before House Republican leaders: Are you in or are you out?

Indiana’s Mike Pence, chairman of the Republican Conference, was adamant. “You betcha,” he said, deploying a Minnesota catch phrase.

But Minority Leader John Boehner won’t have his name on the caucus list.

And Virginia Rep. Eric Cantor and his chief deputy, Rep. Kevin McCarthy of California — known as “Young Guns” for the GOP — are undecided.

Minnesota’s Bachmann, a favorite of the tea party movement, earned approval from the Democratic leadership for her caucus late last week. It came as a bit of a surprise to her leadership, whom she didn’t forewarn before formally applying to create the caucus.

“It was something we were doing on our own,” Bachmann spokesman Dave Dziok said. “Ultimately, we just pulled the trigger.”

Indeed, the tea party movement is a loaded political weapon for Republicans heading into the midterm elections.

Until now, they have had the luxury of enjoying the benefits of tea party enthusiasm without having to actually declare membership. But now that Bachmann has brought the tea party inside the Capitol, House Republican leaders and rank-and-file members may have to choose whether to join the institutionalized movement.

It’s easy to see why some Republicans may be hesitant, even as the tea party, itself, fights over the sentiments expressed by the movement’s most extreme elements.

The Tea Party Federation expelled its most prominent faction, the Tea Party Express, after a spokesman wrote a racially charged letter framed as a satirical jab at Ben Jealous, president of the National Association for the Advancement of Colored People. The Tea Party Express fired back, with a spokesman calling the decision “arrogant and preposterous.”

“If there are some tendencies in the outside movement that you don’t want to be associated with, this could be a risky step,” said Celia Carroll, a political science professor at Hampden-Sydney College who has done academic research on congressional caucuses.

Joining caucuses is somewhat of a ritual in the House, where niche groups like the Sportsmen’s Caucus or the Armenian Caucus are supposed to give lawmakers a chance to build their political identity and promote their own ideas and those of allies outside Congress. The Senate is less relevant in the caucus debate: There is only one officially recognized caucus, the Senate Caucus on International Narcotics Control.

“I think caucuses represent an opportunity for members to get together and to share ideas, and my hope is that this Tea Party Caucus would do the same and also would be an avenue for bringing some of the energy and enthusiasm and the focus that I’ve seen from the national march on Washington, where I spoke on 9/12, [and] traveling around Indiana and a little around the country, deeper into the well of Congress,” Pence said.

Pence is widely viewed as a potential candidate for statewide, or perhaps national office, and he has built on his connection to the movement, which could be politically beneficial in the future.

But the question is not as clear-cut for other Republican leaders.