Rep. Ron Paul's third White House bid is another long-shot attempt because of lingering questions about his viability in a Republican primary and beyond.
Doubts also exist about the Texas Republican's level of tea party support. The more mainstream presidential candidates have co-opted portions of his fiscal message as they also work to woo grass-roots activists who had been seen as Paul's natural constituency.
It's not clear whether Paul, who on Friday became the only Member to officially join the race, would be a 2012 factor beyond his demonstrated abilities to raise money and score debate points.
The eight-term Congressman's libertarian view of the federal government is considered less fringe now than it was during his 2008 White House bid, following the 2010 rise and subsequent influence of the tea party and an ongoing national fiscal crisis that has focused voters' attention on the $14 trillion federal debt. Yet Paul, 75, is no longer the lone Republican voice to advocate for dramatically reducing the size and scope of government.
The others in the race are better-organized candidates who are likely to be perceived by primary voters as more formidable against President Barack Obama. Rep. Michele Bachmann (R-Minn.), a tea party favorite, could further complicate Paul's prospects should she run, although GOP strategists say the Congressman's support within the conservative activist movement is overblown to begin with.
"Ron Paul voters aren't necessarily tea party people," said a Republican strategist who worked for a GOP presidential candidate in 2008. "He had his own little niche, so he doesn't necessarily impact Bachmann. Plus, Bachmann has the advantage of being the candidate the Christian right gets behind. Paul doesn't."
Paul's social views could be considered liberal. He argued in a debate this month, for example, that government should stay out of the bedroom when it comes to the gay marriage debate. He also favors legalization of drugs.
Ryan Hecker, a Houston Tea Party board member who helped launch www.MyTeaParty.org, said Paul would add an attractive voice to the GOP presidential primary contest, but he suggested Paul might have less appeal with this disparate coalition of political activists than some might think.
"I don't see him becoming the monolithic tea party candidate. There is a certain segment of the tea party movement that likes him, but it's not overwhelming," Hecker said. "I think there is definitely a libertarian-versus-conservative divide there, and there is also a viability issue for those who are contemplating his candidacy."
It is extremely rare for a sitting House Member won the presidency, although former House Members who went on to serve as governor, Senator or vice president have won the office. Paul served in the House as a Republican in the 1970s and 1980s before making his first bid for president in 1988 on the Libertarian ticket. He ran again in 2008.
Paul raised tens of millions of dollars for his 2008 bid — more than some of the candidates who ultimately outperformed him in crucial primary states. He was a GOP pioneer in Internet fundraising and has since maintained a fervent following of grass-roots supporters who have helped him win straw poll victories, including at this year's Conservative Political Action Conference.
Paul campaign spokesman Jesse Benton said his boss will run a 50-state campaign, with particular focus on Iowa, Nevada and New Hampshire. Benton dismissed suggestions that Paul's impact on the race would be negligible, asserting that the GOP's direction since 2008 has opened a natural leadership spot for the Congressman.
"It's a positive thing that there are more voices communicating what Ron has been saying his whole political career. Ron stands ready to capitalize on that," Benton said. "We're running to win."
In 2008, Paul scored 10 percent of the vote in the Iowa caucuses and 8 percent in New Hampshire. He placed second in Nevada and fifth in South Carolina.
Republican campaign strategists remain skeptical of Paul's viability in 2012, despite a political climate that could boost the appeal of his message on fiscal and economic policy. That is partly because his views on foreign and social policy remain problematic with much of the GOP electorate. He wants to withdraw troops from Afghanistan, for example.
And winning the tea party vote will be a goal for each candidate, not just Team Paul.
Former Minnesota Gov. Tim Pawlenty has been wooing tea partyers and joined Paul and wealthy businessman Herman Cain (Ga.) at a recent tea party convention.
"The tea party hard right factor is higher than it was in 2008," said a Republican operative based in Washington, D.C. "But there are also several candidates, including Bachmann, who split that vote."
Hecker cast doubt on the notion that there will be a "tea party candidate" in the GOP presidential primary and said Bachmann faces some of the same doubts among tea party activists as Paul.
"I think it's going to be very hard to find a candidate who unites the movement," Hecker said.
As for Bachmann, "There are a lot of people in the movement that like her. There are some who are very passionate about the movement. I think there are others who question her viability and her experience."
Ambreen Ali contributed to this report.
Correction: May 16, 2011
The article's reference to the $14 trillion federal debt has been corrected in the online version. The article also gave incorrect information about how often a sitting House Member won the presidency. President James Garfield was elected while serving in the House.
Senate Minority Leader Mitch McConnell, R-Ky., carries a musket on stage as he speaks during the American Conservative Union's Conservative Political Action Conference (CPAC) at National Harbor, Md., on Thursday March 6, 2014.