Republicans, as everyone knows, are advocates of "states' rights," the theory being that power residing in the hands of the federal government is inherently suspect, while power spread out among 50 smaller governments is inherently virtuous — or at least more so. After all, aren't states "laboratories of democracy," where all kinds of interesting experimentation can take place and the best ideas can then bubble up to the rest of the country?

Well...sometimes. The truth is that conservatives like states having independence when they like what the states are doing, and liberals feel the same way (the difference is that liberals don't claim they have a philosophical commitment to states' rights over federal rights in the abstract). When states' rights collide with a policy objection, the policy objection is going to win.

Usually, that is. But there's at least one area where the GOP is divided on the whole states' rights issue. New Jersey Gov. Chris Christie earlier this week highlighted the disagreement with some blunt words about legalized marijuana. "If you're getting high in Colorado today, enjoy it," he said. "As of January 2017, I will enforce the federal laws." Chris Christie, in other words, is coming to harsh your buzz — or he would be, if he had any chance of actually becoming president.

His position isn't an unreasonable one. While the Justice Department has discretion in how vigorously it enforces the law, and can decide to allow state legalization to take effect unimpeded, federal law is supreme over state laws, and marijuana is still illegal under federal law. And it's not just Colorado — Washington, Oregon, and Alaska also have legalized recreational marijuana use, and there's a good chance that half a dozen other states will follow them via ballot initiatives in the 2016 election, the most notable of which is California.

While this issue hasn't gotten much attention in the presidential race so far, it's one of the few where you'll actually find some diversity of opinion among the GOP candidates. Marco Rubio seems to agree with Christie; though he's a little vague, he says that "we need to enforce our federal laws." Scott Walker's position is essentially the same. Ted Cruz thinks it's all right for the federal government to leave states alone on this issue, but he says that should be Congress' decision, not the president's. Jeb Bush has said about legalization in those states, "I thought it was a bad idea, but states ought to have the right to do it." Rick Perry says much the same thing: States that legalized "will look back and they will find that it was a huge error that they made," but his commitment to the Tenth Amendment is such that he'll "defend it to my death, if you will, to allow them to make those decisions."

Rand Paul has gone the farthest: While he doesn't support legalization, he has co-sponsored a bill to end the federal ban on medical marijuana and has advocated an end to harsh criminal penalties for possession.

With the sort-of-but-not-really exception of Paul, all the Republicans want to make clear that they're opposed to anyone smoking pot. That might be perfectly sincere, but it also reflects their party's demographics and its role in the culture war. To the prototypical Republican — particularly the Republican primary voter — marijuana is something hippies do.

But within the party, that feeling is far from universal. In a recent Pew Research Center poll, 39 percent of Republicans favored legalization. That's significantly less than the 59 percent of Democrats who agreed, but it's still a substantial chunk of the party — and up 15 points from what Pew showed just five years ago. So as strange as it may seem, within a few years a majority of Republican voters might actually favor legalization.

As I wrote last week, Hillary Clinton has been somewhat tentative in her remarks on this topic, saying that we should wait and see how things turn out at the state level before we decide whether it's a good idea to legalize pot on a broader scale (Bernie Sanders takes the same position). That shows how politicians often lag behind public opinion, and it's not unexpected; a few years ago, the idea that a serious presidential candidate might come out in favor of marijuana legalization would have been considered crazy.

But if more and more states legalize cannabis, it could mean that even today's most common Republican position — I don't like it, but I'm not going to fight it — could wind up being de facto support for legalization, at least in the half of the country where liberals are in charge. And if public opinion keeps moving in this direction, don't be surprised if the Democratic nominee in 2020 — and the Republican nominee within another election or two after that — actually comes out in favor of legal pot.