Not long ago, Karl Rove was considered a political genius. His mastery of the small, clever maneuver--typically unappreciated until it swung an election--was a big reason why. To his enemies, nothing exemplified Rovean perfidy like the state ballot initiatives he encouraged banning gay marriage that appeared across the country in 2004. Rove's idea was that conservatives lukewarm on President Bush could be persuaded to support the ban--and, once they'd shown up to do that, would probably vote for Bush, too. On Election Day, the ballot initiatives passed easily and Bush narrowly won a second term.

I have a short piece in the current Atlantic about the marijuana ballot initiatives sweeping the country. (Paul Starobin also has an excellent cover story in National Journal.) But one issue nobody has examined is what effect these initiatives have on candidates' performance at the polls. Acting on a tip from an Obama official, I found a few Democratic consultants who have become convinced that ballot initiatives legalizing marijuana, like the one Californians will vote on in November, actually help Democrats in the same way that gay marriage bans were supposed to have helped Republicans. They are similarly popular, with medical marijuana having passed in 14 states (and the District of Columbia) where it has appeared on the ballot. In a recent poll, 56 percent of Californians said they favor the upcoming initiative to legalize and tax pot.

The idea that this helps Democrats is based on the demographic profile of who shows up to vote for marijuana initiatives--and wouldn't show up otherwise. "If you look at who turns out to vote for marijuana," says Jim Merlino, a consultant in Colorado, which passed initiatives in 2000 and 2006, "they're generally under 35. And young people tend to vote Democratic." This influx of new voters, he believes, helps Democrats up and down the ticket.

The legalization movement appears to be gaining steam. As many as a half dozen states could consider the issue this fall. If the correlation Merlino describes really exists, then Democrats will have an advantage in those states. Does it?

Political scientists disagree about whether gay marriage bans helped Republicans, though a growing body of scholarship suggests that they probably did. So far, nobody has measured marijuana's effect at the polls. But Stephen Nicholson, a leading expert on ballot initiatives at the University of California at Merced, told me that he plans to. What's more, he sees an intriguing precedent in the nuclear freeze initiatives of 28 years ago, which he has studied. "In the 1982 midterms, 10 states had ballot initiatives on the nuclear freeze," Nicholson told me. "This had a significant positive effect on Democratic candidates." In states without them, candidates saw little to no effect.

If Democrats in California and other places where marijuana is on the ballot outperform candidates in states with no initiatives, that may be a clue as to why. And if indeed that happens, might it also presage a Rovean effort among Democrats to give Obama a lift by pushing more state initiatives in 2012?