A staunch social conservative perhaps best known for leading the charge against President Bill Clinton during the 1998 impeachment hearings, former Republican Congressman Bob Barr is the 2008 Libertarian Party nominee for president.

A former federal prosecutor, Barr represented Georgia's 7th District in the U.S. House from 1995 to 2003. He was a senior member of the Judiciary Committee, vice chairman of the Government Reform Committee and a member of the Committee on Financial Services.

In 2002, Barr left Congress and the Republican Party, strongly criticizing President Bush's handling of the Iraq war and what he saw as the government's infringement on social liberties.

Barr's entry into the presidential race was met with some GOP concern that he might do to Sen. John McCain's Republican bid what some say Ralph Nader did to the Democrats in 2000: become a spoiler. Still, Barr maintains that he has a chance to win the White House.

When a Newsweek interviewer pointed out that third-party candidates win very few Electoral College votes, Barr replied, "History provides no blueprint for the future of politics."

Campaign staffers for Democratic hopeful Sen. Barack Obama have acknowledged the potential impact Barr could have on the race in Obama's favor, particularly in Alaska and Georgia.

Alaska is "one of the states where we think Barr can get 6,7, 8 percent," Obama's campaign manager David Plouffe told reporters in late June, according to Politico.

Some GOP leaders, however, are less concerned about the Barr effect.

Former House Speaker Newt Gingrich told the Associated Press that voting for Barr would be the same as voting Obama, and said he's confident most GOP voters will understand that.

"No reasonable conservative is going to vote for anyone except McCain," Gingrich said.

Barr has been a National Rifle Association board member since 1997, and he was a member of a project addressing privacy and security at Harvard University's Kennedy School of Government from 2003 to 2005.

Before joining Congress, Barr worked for the CIA from 1971 to 1978. President Ronald Reagan appointed him to serve as U.S. Attorney for the Northern District of Georgia, which he did from 1986 to 1990.

-- By Meghann Farnsworth, Online NewsHour