

Why is this man smiling? Perhaps because he, the outspoken Rep. Ron Paul (R) of Texas, has the most engaged and vocal following of any of the Republican presidential candidates, despite consistently trailing Texas Gov. Rick Perry and former governor of Massachusetts Mitt Romney in the polls. Scott Audette/Reuters/File
In this undated photo, Ron Paul appears in uniform. He was a flight surgeon in the Air Force from 1963 to 1965 and then served in the Air National Guard from 1965 to 1968. Called the "intellectual godfather" of the Tea Party movement, Mr. Paul espouses libertarian ideas that often differ from both Republican and Democratic Party stances. Courtesy of Ron Paul Campaign/File
Ron Paul talks with President Ronald Reagan in this undated photo. Ron Paul was one of only four sitting House members to back Ronald Reagan in his 1976 presidential run. Mr. Paul served in Congress as a US representative of Texas from 1976–77, then from 1979–85, and finally from 1997 to the present. He has run for president twice before, in 1988 and 2008. Courtesy of Ron Paul Campaign/File
Ron Paul defeated Democrat Loy Sneary in the Texas 14th district congressional race in the Nov. 3, 1998 election. Born in Pittsburgh, Pa., Mr. Paul worked as an obstetrician and gynecologist during the 1960s and 1970s, delivering more than 4,000 babies before entering politics in 1976. AP/File
Jon Stewart (r.), host of the sardonically irreverent and liberal-leaning 'The Daily Show with Jon Stewart,' has been an unlikely champion of Ron Paul throughout his campaign, claiming Mr. Paul is unfairly ignored by the media. Ronald Smits/PictureGroup/AP/File
Republican presidential candidate Ron Paul (l.), Texas Gov. Rick Perry (c.), and former Massachusetts Gov. Mitt Romney greet each other prior to a debate in Orlando, Fla., on Sept. 22. John Raoux/AP/File
Ron Paul supporters celebrate their second place finish in the Georgia Republican Party's fish fry in Perry, Ga., on Aug. 27. Businessman and radio show host Herman Cain won the ballot with 232 votes, Ron Paul was second with 229 votes, and Texas Gov. Rick Perry was third with 180. Beau Cabell/The Macon Telegraph/AP/File
Presidential hopeful Ron Paul waves his arms as he arrives to a crowd of several hundred who came to see him in Concord, N.H., on Aug. 17. Jim Cole/File
Supporters cheer Republican presidential candidate Ron Paul after he spoke at the Republican Party's Straw Poll in Ames, Iowa, on Aug. 13. Charlie Neibergall/AP/File
Republican presidential candidate Ron Paul and his wife Carol wave to the crowd after his speech at the Iowa Straw Poll in Ames, Iowa, on August 13. Jim Young/Reuters/File
Presidential hopeful Ron Paul is embraced by a supporter after appearing on NBC's 'Meet The Press' in Washington on Dec. 23, 2007. Gerald Herbert/AP/File
Supporters of Ron Paul wave banners before the start of the Univision Republican Presidential Candidate Forum at the University of Miami in Coral Gables, Fla., on Dec. 9, 2007. Luis M. Alvarez/AP/File