WASHINGTON (CNN) - Bob Barr was once a loyal soldier in the Republican Party - a lawmaker GOP leaders could count on to return home each weekend and echo their talking points at local political events, town hall meetings and civic lunches.
As a young political reporter in Marietta, Georgia, I often heard Barr serve up generous helpings of Republican doctrine over buffet lunches and chicken dinners.
For Republican leaders such as House Speaker Newt Gingrich, who represented a neighboring district, Barr was a dedicated warrior. And he remained so even after he lost a primary fight in 1992 to colleague John Linder, a battle set up by redistricting.
But a few years later, Barr went AWOL from the Republican Party - or, as he tells it, the GOP abandoned him.
He is now the Libertarian Party's presidential nominee and is crisscrossing the country promoting its principles and hunting for votes.
So why did Barr abandon the Republican Party in 2006?
"It probably wasn't any one thing," he said during our conversation last week outside the White House.