Washington (CNN) - When the Senate Tea Party Caucus convenes for the first time Thursday, one of the movement's biggest stars will be noticeably absent.
Alex Burgos, spokesman for Republican Florida Sen. Marco Rubio confirmed the event is not on the senator's schedule, but said he has not made a decision regarding caucus membership.
"Senator Rubio is proud of his relationship with the tea party movement and shares its commitment to tackling debt, defending the free enterprise system and restoring our limited government tradition," Burgos said in an e-mail to CNN. "Ultimately, he hopes Floridians will judge him on his voting record and his commitment to delivering on the promises he made through the campaign."
Burgos added that Rubio will join the Senate Steering Committee, a group chaired by South Carolina Sen. Jim DeMint that meets regularly to promote conservative policies and legislation.
Rubio, who received early support from the Tea Party, told the Florida conservative blog "the Shark Tank" that he's "concerned" the Tea Party is abandoning its roots.
"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 the sudden becomes some sort of movement run by politicians," Rubio said.
The freshmen senator who won a three-way race in November against independent Gov. Charlie Crist and Democratic Rep. Kendrick Meek, said the power of the Tea Party comes from its "ability to drive the debate and issues from the grassroots up, as opposed to from the politicians down."
The meeting of the Caucus was announced by DeMint, Kentucky Sen. Rand Paul and Utah Sen. Mike Lee, all of whom enjoyed backing from the conservative faction during the midterm elections.
Amy Kremer, Chairman of the Tea Party Express said she's "very disappointed" in Rubio.
"When you rose to victory with the help of the people within the Tea Party movement, I think a lot of people are disappointed over it," Kremer told CNN. "But ultimately he's going to be judged on how he votes, and if he doesn't vote the way people want him to his term will be limited here."
Kremer, who plans to speak at the meeting, said new members are mistaken if they think they can "straddle the fence" between different groups in the Senate.
"If they don't vote the way we want, they will be voted out," Kremer said.