WASHINGTON -- Sen. Bill Nelson was giving a passionate speech about the danger of pythons in the Everglades, TV cameras rolling. Standing off to the side, silently, was a man who exuded all the anonymity of a mid-level legislative aide.

It was Florida's other U.S. senator, George LeMieux.

The fleeting scene on the Senate floor Wednesday reaffirmed the caricature of LeMieux as the accidental senator, a mere custodian until his former boss, Gov. Charlie Crist, can assume the position.

In reality, the 40-year-old Republican is trying hard to seem anything but a placeholder.

A month after being appointed to replace retired Sen. Mel Martinez, LeMieux has worked to inject himself into oil drilling, healthcare and Cuba policy issues. He has been an aggressive user of new media formats such as Twitter and YouTube, trying to cultivate an image as a tireless, knowing legislator.

LeMieux delivered the weekly Republican radio and Internet address Saturday, a high profile platform that he used to criticize aspects of the Democratic healthcare reform effort, including cuts to Medicare. On Wednesday, he plans to deliver his first speech on the Senate floor, outlining a set of priorities for his tenure. (For now, he is keeping a lid on the details.)

``I don't think anybody who knows me would think that I would be a seat warmer,'' LeMieux said Thursday as he returned to his sprawling office from the Capitol. ``My goal is to get six years' worth of work done in 16 months.''

He is at once in an enviable and awkward position, chosen by Crist over a host of better known stand-ins, some with extensive experience in Congress. Few doubt LeMieux's intelligence or political skill, but the move struck many as cronyism. LeMieux faces the challenge of not only trying to allay those critics in Florida but also to be taken seriously on Capitol Hill, where he is the youngest current member of the Senate.

LeMieux stepped into an elevator and was greeted by 76-year-old Sen. Bob Bennett, R-Utah. ``You know you're important when you come trailing a herd of reporters,'' Bennett said. LeMieux laughed and replied, ``a herd of one.''

He is not garnering big-time attention, but LeMieux and his staff have worked to get him into the news as much as possible, issuing the requisite stream of news releases and also venturing into video and producing fodder for political blogs. Last week, LeMieux posted a national debt clock outside his office.

He says his concern about the debt is rooted in the future of his three young boys, Max, Taylor and Chase. LeMieux and his wife, Meike, are expecting a fourth child. Over the weekend the family moved from Tallahassee to Washington, where they are renting a home near American University.

OFF TO A FAST START

LeMieux has quickly, if not audaciously, used the rules of the Senate to his benefit. He placed a ``hold'' on legislation that would expand oil drilling and cut funding to Radio and TV Martí, which broadcast into Cuba. Because the Senate operates under unanimous consent, one member can slow things down.

At first glance, LeMieux's concern over oil drilling seemed in line with those of Nelson and Martinez, who have managed to keep the issue at bay. But LeMieux said he is in favor of drilling as long as it is done responsibly, a posture matching that of Crist and other Florida Republicans.

He said he wants to make sure any legislation provides Florida with some of the profit. LeMieux's freshly filed financial disclosure form shows that as a lawyer with Gunster, Yoakley & Stewart in Tallahassee, he was paid at least $5,000 by Florida Energy Associates, a group pushing oil drilling among state lawmakers. LeMieux declined to comment Thursday, citing attorney-client privilege, and the head of the group did not return a phone call.