Sen. George LeMieux (R-Fla.) may have come to Capitol Hill earlier this year largely to fill in for retired Sen. Mel Martinez (R) until next year’s election and keep the seat warm for his ex-boss, Gov. Charlie Crist (R), who is running for the seat. But he’s certainly begun acting like someone looking to make his stay in Washington, D.C., more permanent.

Far from acting simply as a caretaker, LeMieux has become an increasingly active member of the Senate’s GOP ranks — for instance, he recently joined Minority Leader Mitch McConnell (Ky.) and other leaders at a news conference castigating Democratic health care reform plans. Even the Democratic National Committee has taken note of LeMieux, leveling attacks against his statements on the health care debate in recent days.

And on Tuesday, LeMieux will have the first fundraiser for Protect America’s Future PAC, his newly created leadership political action committee.

Leadership PACs are not unusual in the Senate — most lawmakers set up the fundraising organs to indirectly help their own re-election bids as well as to funnel funds to other candidates.

But given his presumed short-term status in the Senate, LeMieux’s decision to set up the PAC has raised some eyebrows around Washington.

In an e-mail sent to K Street donors and other GOP financial backers Thursday morning, lobbyist and Republican strategist T.J. Petrizzo invites recipients to a “reception and/or dinner on behalf of the Protect America’s Future PAC.—

Petrizzo also praises LeMieux’s work in the Senate and says that while he is not seeking election to the seat he currently holds, “Senator LeMieux is also working to do his part in electing more Republicans from across the nation to serve in the U.S. Senate come January 2011— by setting up the PAC.

Petrizzo was not available for comment Thursday afternoon, and a request for comment from LeMieux’s office was not responded to.

While LeMieux may not be looking to run for election next year, rumors have already begun in Florida that he may have decided the Senate is a nice place after all, and he may throw his hat in the ring in 2012 to challenge Sen. Bill Nelson (D-Fla.).

Crist, LeMieux’s former boss, was originally the overwhelming favorite in the 2010 Florida Senate election, but he is facing a very spirited Republican primary challenge from former state Speaker Marco Rubio. Rep. Kendrick Meek is the leading candidate on the Democratic side.