Rick Santorum’s campaign is running robocalls urging Democrats to vote for him in Michigan’s GOP primary after Santorum a month ago said only Republicans should vote in the party’s primaries.

CNN reported on Tuesday that during a telephone town-hall event on January 29th, Santorum argued that participation in Republican primaries should include only GOP voters

"We want the activists of the party, the people who make up the backbone of the Republican Party to have a say in who our nominee is as opposed to a bunch of people who don't even identify themselves as Republicans picking our nominee," Santorum said in a telephone town-hall on January 29th according to CNN. "I don't like that. I believe that states should only allow Republicans to vote in Republican primaries."

The CNN report came the day of the Michigan Republican primary and a day after Santorum's campaign said it was pushing a robocall in Michigan urging Democrats to vote for Santorum in the primary. In Michigan, voters can vote in either primary if they are of the opposing party.

"It's the Republican nomination, not the independent nomination or the Democratic nomination," Santorum added during the call. "If you're a Democrat and you want to be a Democrat, then vote in the Democratic primary, not the Republican. If you want to vote in the Republican Party then become one."
 
On Tuesday, Mitt Romney and Santorum exchanged criticism over the calls. Romney said the former Pennsylvania senator's campaign had resorted to "dirty tricks." Meanwhile Santorum defended the robocall saying it was meant to "prove the point we can attract voters we need to win states like Michigan," according to ABC News.

The Santorum campaign did not immediately respond with a comment.