Ron Paul , a Texas physician and member of the U.S. House of Representatives, has a back-to-basics approach highly esteemed by the conservative Tea Party movement.

Paul, 76, has served three separate stints in the House and announced earlier this year that he will not run for congressional re-election, so he could focus on the race for the presidency.

Paul is known for his libertarian ideas, which often differ from those of both Democrats and Republicans. Libertarians emphasize individual freedom and limitation of government. Paul has founded an advocacy group, Campaign for Liberty , which endorses strict adherence to the U.S. Constitution, a noninterventionist foreign policy. He also has advocated ending the U.S. Federal Reserve system.

Paul says he favors wiping out all income tax, arguing that the government has no right to an individual's earnings. He has said he endorses free trade, but not regional trade organizations such as NAFTA.

Experts say his unique viewpoint may keep him from getting the Republican nomination, but they note that because of his popularity with the Tea Party and a band of extremely loyal followers, his views are helping to shape the Republican agenda.

Faiz Shakir of the Center for American Progress notes that Paul “has views on foreign policy that no one else in the campaign has, which is that we should not be engaged in foreign entanglements.” Paul advocates removing troops from foreign deployments, cutting the defense budget, and cutting aid for Israel.

Brian Darling of the conservative Heritage Foundation says he believes Paul has been “an excellent force for good” in the Republican Party. While he does not expect Paul to win the nomination, he says, “You're seeing other candidates adopt Ron Paul's positions on reforming the Federal Reserve, in monetary policy, and in economic policy.”

Seen as a purist in the murky world of politics, Paul has attracted a loyal grassroots following and is popular among young people. He has twice run for president, in 1988 as a Libertarian candidate and in 2008 as a contender for the Republican nomination. Paul dropped out of the race in 2008 to establish his advocacy group.

Paul's son Rand Paul is a U.S. senator for the southeastern state of Kentucky. He, too, is supported by the Tea Party movement. The Pauls are the only father-and-son team serving in Congress at the same time.

Paul has been married to his wife, Carol, since 1957. In addition to Rand Paul, they have four other adult children.