[cnn-photo-caption image= http://i.cdn.turner.com/cnn/2008/images/04/03/art.barr.gi.jpg caption="Bob Barr will announce a presidential run Monday."]
WASHINGTON (CNN) – Former Republican Rep. Bob Barr will announce Monday that he will run for president as a Libertarian, a source close to the Georgian told CNN.
Barr will officially declare his candidacy at a news conference at the National Press Club in Washington. The four-term congressman left the GOP in 2006, saying that Republicans had "lost their core principles."
Barr made a name for himself in Congress for his ardent conservative philosophy and his role in President Clinton's impeachment. He lost a primary election in 2002.
Last month, Barr formed a presidential exploratory committee as he weighed a run for the White House. The source said that Barr had been considering a presidential bid "for several months. He currently runs Liberty Strategies, a consulting firm in Atlanta and Washington.
Barr joins a handful of other candidates seeking the Libertarian Party's presidential nomination including former Alaska Sen. Mike Gravel, who unsuccessfully sought the Democratic presidential nomination this year. Libertarians meet in Denver on May 22 for a four day convention where members will choose the party's presidential nominee.