Democrats for Rick Santorum?

It may be strange for Democrats to cast their ballot for a man who is pro-life, anti-gay rights and a card-carrying member of the Tea Party.

It may seem even more bizarre that the former Republican Pennsylvania governor blasted robo-calls in Michigan leading up to that state's presidential primary, which is open to Democrats, and asking Democrats to vote for him.

In exit polling of Michigan primary voters, 53 percent of Democrats who participated in the primary cast their ballot for Santorum, according to CNN.

The other three contenders for the GOP nomination - frontrunner and former Massachusetts Gov. Mitt Romney, former House Speaker Newt Gingrich and U.S. Rep. Ron Paul (R-Tex.) couldn't muster more than 20 percent of Democratic support.

The strong Democrat support for Santorum in the contest made the Michigan race tighter, with Romney taking the primary, 41.1 percent to Santorum's 37.9 percent.

But there's a method to this madness.

The reason? Strategic voting.

Democrats view Santorum, the stiffest challenger to Romney for the nomination, as by far the most conservative of the four remaining Republican candidates and the weakest candidate in a head-to-head matchup with President Obama.

Santorum's campaign could not be immediately reached for comment.

So obviously they would have loved to see a Santorum victory in Michigan and will do whatever they can to make it more difficult for Romney to secure the nomination.

According to a Real Clear Politics calculation of a handful of polls, Obama does best head-to-head against Gingrich, who he is beating nationally by an average of more than 12 percent.

After Gingrich, polls show the president would like Paul to be the GOP nominee, with Obama leading the Texas congressman by more than 6 points.

In a hypothetical Obama-Romney contest, the president has a four-point lead.

Democrats can do the most damage in open primaries, where every state voter is eligible to participate.Luckily for Santorum, four of the eight upcoming primary contests on Super Tuesday are of the open variety: Georgia, Tennessee, Vermont and Virginia.