Beach said the popular perception that prisons are packed with people who have done nothing more than possess marijuana is a myth. He said the enforcement of drug prohibitions, while expensive, has succeeded in reducing drug use, particularly among children, and drug-related violence. He argued that legalization would not eliminate the black market for drugs but would empower dangerous drug cartels. He predicted unforeseen consequences from the recent legalization of recreational marijuana in two states.

But few seemed to be buying it.

In recent years, American public opinion has shifted rapidly in favor of legalizing marijuana. The percentage of adults who support it has gone from 12 percent in 1969 to 58 percent as of last fall, according to Gallup; in the past decade alone, support for legalization has increased by 24 percentage points. The shift has powered a wave of political victories for marijuana advocates, from the 20 states where medical marijuana is now legal to the unprecedented ballot measures legalizing the drug in Colorado and Washington in 2012. Three more states expect to put pot to a popular vote this year, with referenda on medical marijuana in Florida and full legalization in Oregon and Alaska.

What opposition remains is concentrated among Republicans. According to Gallup, only about a third of Democrats and independents now oppose legalization, compared to nearly two-thirds of Republicans. Opponents of legalization are also disproportionately elderly. The situation closely parallels the party's predicament on gay marriage, which most Republicans still oppose even as widening majorities of the broader public support it.

It adds up to a quandary for the GOP: Should it embrace the unpopular position still disproportionately favored by its members and risk marginalization as a result? Or will the burgeoning conservative voices in favor of legalization win out? Simply put, do Republicans want to be on the losing side of yet another culture war?

For the CPAC panel's audience, which was passionate and disproportionately young, the answer was clearly no. College students wearing "Stand With Rand" stickers in honor of the libertarian-leaning Kentucky Senator Rand Paul expressed their distrust for marauding government agents; a cowboy-hatted former policeman in a "Cops Say Legalize Pot" T-shirt asked Beach, "How do you justify morally the deaths of dozens and dozens of kids on your altar of prohibition?" A writer for Reason magazine cited good results from legalization in Portugal.

One questioner took a personal swipe at Beach's boss, alluding to the decade-old revelation that Bennett lost millions gambling to ask whether Beach thought gambling should also be banned. "I'm not going to touch that," Beach said nervously.

Ham, who frequently spars with the Fox News anchor Bill O'Reilly on the subject, argued that the truly conservative position is to let people make their own choices and to avoid wasting taxpayer dollars enforcing laws that don't seem to work and that often have negative consequences. Even if legalization ends up having unanticipated bad effects, she said, those should be weighed against the lives no longer ruined by the drug war and the "moral value" of increased freedom.