Rick Santorum at his Iowa caucus victory party in Jan. 3. (Charlie Riedel/AP)

A colleague called the Republican National Committee the other day and was told by a spokesman there that it was closed.

Then a longtime state GOP official said no, it ‘s “semi-closed.” That means it’s pretty much open.

Here’s how it works: voters walk into the polls and are asked to declare whether they want a Democratic ballot or a Republican ballot. They can pick either and then vote.

Now, under a new state rule, your choice will be record ed and public information — and could subject you to annoying robo-calls, vendor solicitations and such. Also, you’d have some explaining to do if you run for office in the future. But that’s about it.

And crossover voting is not uncommon in Michigan. Hard to quantify, but some veteran Michigan Democrats believe such voting may have been either responsible for Sen. John McCain’s primary win over former President Bush in 2000 or certainly padded his total vote. There was, in fact, an effort among the libs to organize a crossover campaign.

More recently, Michigan’s Republican Governor Rick Snyder won the 2010 four-way primary apparently with hefty support from Democrats unhappy with the two Democratic primary contenders — one was seen as ultra-liberal, the other as moderate but mildly anti-choice.

So they opted instead to vote on the GOP ballot for Snyder, we were told, whom they saw as the only moderate on that ballot.

There don’t seem to be clear signs yet of any effort in state — orchestrated or not — by Democrats to embarrass Romney in his home state by voting for Rick Santorum or another opponent. (Even if they wanted to, the Democrats probably couldn’t figure out which other candidate to vote for.)

On the other hand, in the age of social media, these things can gel quickly, very quickly. The popular liberal blog Daily Kos posted a call Wednesday on Facebook for Democrats to crossover for Santorum in Michigan and other states with open primaries or caucuses.

The move is called “Operation Hilarity.”