One more note on the possibility of Democrats voting in the GOP primary… in 2000, when Michigan voted, Al Gore had already knocked around Bill Bradley like a piñata and the Republican race had pretty much come down to George W. Bush vs. John McCain.

McCain was running heavily on campaign finance reform – an idea supported by many liberals – and his cheering section in the mainstream media had persuaded, apparently, a significant number of Democrats that McCain was a better choice than Bush.

But this year, there doesn’t seem to be a clear choice for Democrats crossing over. Markos Moulitsas is urging Democrats to vote for Romney. Some Democrats might still be backing McCain, but you could also see some of them attracted to Huckabee’s populist themes. Some might even want to back the vocally anti-war candidate, Ron Paul.

McCain’s not counting on them:

McCain dismissed the idea by imagining what a “liberal Democrat” in Michigan might be thinking. “Oh, gee. I’ll go find out where the polling place is, drive down, take my lunch hour or whatever it is, so I can vote for one of these jerk Republicans.” He said some might do just that, but not enough. “The Republican base is obviously, is clearly, the majority of our efforts.” He also said he’s going after the sizable independent vote there. In Michigan, voters can cast either Republican or Democratic ballots in the primary.

So even if a significant number of Democrats cross over, it’s not clear that they’ll be able to push one candidate who otherwise would have lost over the top.