Four years ago, Rush Limbaugh mounted "Operation Chaos" to encourage Republicans to support Hillary Clinton in Democratic primaries, with the goal of weakening the eventual Democratic candidate. Democrats are now returning the favor, as Michael Shear reports in The New York Times:
Rick Santorum’s campaign on Monday night began urging Democrats to vote against Mitt Romney in the Michigan Republican primary, apparently counting on cross-party support to win a close contest in the state on Tuesday.
With polls in Michigan suggesting a tight race between Mr. Romney and Mr. Santorum, the victory could be determined in part by Democrats and union workers eager to cause mischief in Tuesday’s Republican presidential primary....
The chairman of the Michigan Democratic Party, Mark Brewer, issued a press release last week reminding members of his party that they will still be able to participate in the Democratic caucus on May 5 if they vote as a Republican on Tuesday.
Markos Moulitsas, a liberal blogger, has called for “Operation Hilarity,” in which Democrats vote for Mr. Santorum. “Let’s keep the .G.O.P clown show going!” he said.
Mr. Moulitsas has gotten plenty of push-back from liberals who say the Democrats shouldn’t be playing such games. But he has called the idea a “no brainer,” saying that voting for Mr. Santorum would ensure that the Republican primary contest would be extended.
“The longer this thing drags out, the more unpopular the Republican presidential pretenders become,” he wrote on his blog, Daily Kos.