Former U.S. Rep. Bob Barr won the Libertarian nomination for president Sunday afternoon at the Denver Sheraton.

Barr won on the sixth ballot over longtime Libertarian activist Mary Ruwart 54 percent to 46 percent.

Libertarian National Convention delegates now have to select a vice-presidential candidate. Barr has backed third-place presidential finisher Wayne Allyn Root of Nevada; Root helped Barr secure the nomination by swinging his support to Barr during the last ballot.

"This will be a historic and positive campaign that will succeed," Barr said in his victory speech. "This is a campaign that will win."

Barr was supported by many who believe he can increase the Libertarian Party's stature as he is a nationally known figure thanks to his role in the House impeachment of President Clinton.

But others considered him an interloper whose previous stances on the drug war, gay marriage, and other issues clash with Libertarian Party philosophy.

At a Libertarian presidential debate Saturday night, Barr sought to reassure Libertarian delegates, renouncing his past stances on the drug war and part of the Defense of Marriage Act.

Barr said he expects to be on the November ballot in at least 48 states -- Oklahoma and West Virginia are potential holdouts.

Russell Verney, Barr's campaign manager who also ran Ross Perot's 1996 presidential campaign, said the current political landscape is currently better for a third-party candidate than it was in 1992 or 1996. Perot captured 19 percent of the vote during his 1992 campaign. 

Ruwart had support from many of the party faithful as a longtime Libertarian activist, and impressed many at last night's Libertarian presidential debate.

She's closely identified herself with Republican presidential candidate (and former Libertarian presidential nominee) Ron Paul, and says she can tap into the excitement generated by Democratic presidential candidate Hillary Clinton among female voters.

However, many had concerns about previous statements she made about legalizing child pornography.

Former U.S. Sen. Mike Gravel, who had earlier this year unsuccessfully sought the Democratic presidential nomination, dropped out of the running for the Libertarian nomination on the fourth ballot.

"If you can’t take the horses to water, then they’re just not going to drink any water," Gravel said after he was dropped from the ballot. "They’re not used to realizing that they could win. They’re not used to realizing that they could take the Democrats, take the Republicans. But that’s not going to happen."