You will probably hear a lot tonight, particularly if Rick Santorum is running relatively well in Michigan, about Democrats “crossing over” on the Pennslyvanian’s behalf. And if this is the big story, and results are coming in kinda slow, you will hear an awful lot about how MI Dems did this very same thing in 2000 to help John McCain stay alive against George W. Bush, or how MI Republicans back in the day cast tactical voters for Jesse Jackson and George Wallace.

That’s all well and good, but it’s important to keep several story lines separate. Some Ds crossing over will indeed be tactical voters while some are either vaguely attracted to Santorum or hate Romney so much it’s hard to call their votes truly “tactical” in the sense of cold-blooded efforts to extent the nominating process or produce the weaknest nominee.

And aside from voter motives, there are several efforts to “mobilize” Democrats to crossover on Santorum’s behalf that it is helpful to keep separate. One is by a local Democratic political consultant named Joe DiSano who is sending emails and even paying for robocalls to targeted Democratic households with a simple message of encouraging them to vote to embarrass Romney and help Obama. Another. launhced by blogger Markos Moulitsas, calls itself “Operation Hilarity,” which is also overtly mischief-making, and aims at ginning up no more than a couple of thousand Santorum votes.

Then there are anti-Romney ads being run in the state by the Obama Super-PAC, Priorities USA, which are justifiable as general election positioning.

And at the last minute, the Santorum campaign has launched a robocall campaign targeting Democratic voters, as reported by TPM:

Bill Ballenger, a longtime Michigan politico and the editor of Inside Michigan Politics, spoke with TPM about the call earlier in the day. He said the call piqued his interest because it sounded like it could have come from a union targeting Romney ahead of the Feb. 28 primary. The call focuses on Romney’s opposition to the auto bailout and calls on Democrats to vote for Santorum Tuesday because of it.

“It went on and on like this and I kept listening because I kind of smelled a rat,” Ballenger said. “And finally at the very end, in a tagline it says, ‘this call was paid for by the Santorum for president committee.’”

Thanks to exit polling, you will hear quite precise numbers about Demcratic participation in the primary tonight, but it’s unlikely there will be anything other than anecdotal discussion of crossover motives. The one thing that’s clear is this: Romney’s camp will spin every single Democratic vote for Santorum as insincere and tactical, and Santorum’s will spin every single Democratic vote as proving its candidate’s Reaganesque appeal to the blue-collar voters of the Great American Heartland, blah blah bark bark woof woof. So be forewarned and bring a shovel.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.