"Don't get hung up on purity," Barbour said. "In politics, purity is a loser."
The warning from Barbour, a former Republican National Committee chairman, came amid threats by some tea-party activists to challenge the party's congressional incumbents next year, and with fresh memories of bloody 2010 primaries between tea-party insurgents and establishment figures that may have cost the GOP a couple of Senate seats.
"If you split the conservative vote, that's the best thing for the left," Barbour said.
Four candidates for the GOP nomination addressed the crowd of nearly 2,000 at a hotel next to the Mississippi River on the second day of the three-day conference, which will culminate Saturday in a straw poll of presidential preferences.
Rep. Michele Bachmann of Minnesota, founder of the House Tea Party Caucus, said she could unite the social conservatives and fiscal conservatives in the tea party because she is both.
"Get ready, 2012, the tea party will be bigger than ever," Bachmann said. "The tea party and all of America has one goal, and it is this: that Barack Obama will be a one-term president."
She also said her Republican presidential rivals on the stage during Monday's CNN debate in New Hampshire were all people who "could lead this country."
Three of those rivals - former Sen. Rick Santorum of Pennsylvania, former pizza executive Herman Cain, and Paul - also addressed the conference Friday. Two leading candidates, former Massachusetts Gov. Mitt Romney and former Minnesota Gov. Tim Pawlenty, did not attend. Former Utah Gov. Jon Huntsman, most recently U.S. envoy to China, had planned to appear but canceled because of what his campaign said was illness.
Texas Gov. Rick Perry will address the conference Saturday amid indications that he, too, may decide to join the race. His name is not on the straw-poll ballot, though.
Santorum said he was the most consistent candidate on the need to trim entitlement programs in order to save them, and noted that from the beginning he had supported the plan by Rep. Paul Ryan (R., Wis.) to privatize Medicare. And if Obama's health-care law is not repealed, Santorum said, it would be a "game changer" that would turn the United States into "the country that your ancestors left."
Cain said he would cap the personal and corporate tax rates at 25 percent and reduce the capital-gains tax to zero. "I'm tired of this national nightmare we're on right now," he said. "This economy is not growing."
Paul said it was time for the U.S. government to quit oppressing its citizens, citing laws against selling and consuming raw milk and growing hemp.
He said libertarian ideas were catching on, citing agreement among most of the GOP candidates that it is time to get U.S. troops out of Afghanistan.
"Other candidates are using our language," Paul said.
Contact politics writer Thomas Fitzgerald at 215-854-2718 or firstname.lastname@example.org.