Micah Cohen studies a recent poll (pdf) on the subject:
While polls have found that half, or close to half, of American adults generally oppose legalization, the YouGov poll found that only about a third of respondents favored enforcing federal law in states that had decided to legalize use.
Instead, 20 percent of respondents in the YouGov poll said that they were not sure what the federal government should do, more than double the percentage of adults that polls have usually found to be undecided on the overall question of legalization.
The YouGov poll is just one data point, and more polling will yield a fuller picture. But a portion of American adults who oppose the legalization of marijuana may also be partial to states’ rights, and those two impulses are in tension here.
Allahpundit sees "a rather sweet political opportunity for the GOP":
They’re desperate for ways to earn some goodwill with young voters and minorities. Opposing prosecutions for weed is an easy way to do it, and thanks to Washington and Colorado voters, they wouldn’t have to do it on the merits if they so chose. They could do it purely on federalism grounds — i.e. while opinions on marijuana may differ, it’s disgraceful that Congress would trump the considered judgment of a sovereign state on what its citizens should and shouldn’t be allowed to ingest. I doubt you’d lose many anti-marijuana seniors with a principled argument like that and it would change the framework of this debate enough that it might allow for a bolder decriminalization debate later.
Nate Cohn basically agrees:
If Republicans don’t seize the middle ground on marijuana legalization, Democrats will eventually use the issue to their advantage. Not only will Democratic primary voters demand it, they will have a lot to gain. As more younger, pro-marijuana voters enter the electorate and replace their elders, support for marijuana legalization will continue to increase, absent intervening events that reshape public opinion, like a disastrous ending to the experiments in Colorado and Washington. If marijuana becomes another partisan social issue, like gay marriage or abortion, it will make it even more difficult for Republicans to appeal to millennial voters.
For the longest time, libertarians on the right were among the most anti-Prohibition of all our political factions. William F Buckley himself favored legalizing weed decades ago on the grounds of personal freedom and federalism. This really is an issue which Republicans could and should champion on federalism and freedom grounds, especially if the Obama administration foolishly decides to ramp up the drug war in this case. Go for it, GOP. You have an entire generation to win back.
The Dish 