The Senate Tea Party Caucus met for the first time Thursday as Sen. Jim DeMint (R-S.C.) rebuffed the notion that the caucus would lead to Washington insiders co-opting the grassroots movement. 

"It's not going to be a caucus run by politicians," DeMint told reporters before the start of the group's first official meeting on Capitol Hill. "It's not going to be a sit-down caucus like the Steering Committee that's institutionalized. It's more of a forum than a caucus." 

The group has only four members at the moment — Sens. DeMint, Rand PaulRand PaulTrump phones Senate holdouts on GOP healthcare bill Cornyn: GOP won't delay ObamaCare repeal vote GOP senator: Leadership trying to 'jam' through healthcare bill MORE (R-Ky.), Mike LeeMike LeeTrump phones Senate holdouts on GOP healthcare bill A bipartisan consensus against 'big pharma' is growing in Congress Cornyn: GOP won't delay ObamaCare repeal vote MORE (R-Utah) and Jerry MoranJerry MoranThe Hill's Whip List: Senate ObamaCare repeal bill Proposal to privatize air traffic control struggles to win over critics Senate panel to reject Trump’s air traffic control plan in aviation bill MORE (R-Kansas).

The South Carolina Republican downplayed the group's small membership, saying getting a large number of senators to join isn't the point. 

"What we want to try to do is make [activists] feel like they're part of what's going on," DeMint said. "Remind them that we're listening; we didn't just get elected and forget about them." 

"None of us purports to speak for the Tea Party movement," stressed Lee, who called the Tea Party a "spontaneous, nationwide grassroots political phenomenon."  

Paul said it was the Tea Party that is "co-opting" Washington and not the other way around.

Notably absent was Sen. Marco RubioMarco RubioRubio: 'I hope' Mexican elections won't end partnership against cartels Election hacking fears turn heat on Homeland Security Will Republicans stand up to the NRA's insurrection rhetoric? MORE (R-Fla.), an original Tea Party star who criticized the caucus earlier this week, saying in an interview he doesn't see the need for it and doesn't plan on joining.

"My concern is that politicians all of a sudden start co-opting the mantle of the Tea Party," Rubio said Monday. "If all of a sudden being in the Tea Party is not something that is happening in Main Street, but rather something that's happening in Washington, D.C., the Tea Party all of a sudden becomes some sort of movement run by politicians." 

Asked about Rubio's absence, DeMint said he's not concerned.

"That wasn't the whole point," he said. "We didn't try to get everybody here ... Let's just get it started and see what happens."

At least two other newly elected GOP senators spoke at the meeting — Sens. Pat Toomey (R-Pa.) and Jerry Moran (R-Kan). Toomey has not joined the caucus yet, but Moran, who was a founding member of the House Tea Party Caucus, said after the meeting he would become the fourth member.

Toomey came to speak about his bill to prioritize interest payments on debt, which he said would prevent the government from defaulting on its obligations even if the debt ceiling isn't raised this spring. Toomey slammed the argument put forth by Treasury Secretary Timothy Geithner and the Obama administration that not raising the debt ceiling means automatically defaulting.  

"It is factually untrue and very unhelpful to propagate this myth," he said.

Toomey, Paul, DeMint and Lee offered support to the notion that Republicans should tie a constitutional balanced-budget amendment to any vote to raise the debt ceiling.   

Other prominent conservatives and activists in attendance Thursday included Americans for Tax Reform President Grover Norquist, Tea Party Express Chairman Amy Kremer and FreedomWorks President Matt Kibbe. 

—This story was updated at 1:27 p.m. and 5:13 p.m.

An earlier version incorrectly stated Sen. Ron JohnsonRon JohnsonTrump phones Senate holdouts on GOP healthcare bill The Hill's 12:30 Report Cornyn: GOP won't delay ObamaCare repeal vote MORE (R-Wis.) is a member of the Tea Party caucus.