As the Republican nomination race slogs on, Mitt Romney’s campaign team is hoping that Rick Santorum’s 2008 endorsement of their candidate will help tip the scales.

A video posted last week on Romney’s YouTube page highlights Santorum’s bygone message. “If you want a conservative as the nominee of this party, you must vote for Mitt Romney,” he said during the last presidential election. Romney’s camp must think themselves pretty clever — and are no doubt grateful to Matt Drudge for making it his headline — but this ploy may backfire.

As I pointed out last month, Mitt Romney donated $4,200 to Rick Santorum’s failed 2006 Senate reelection bid. It’s unclear whether Santorum remembers this fact, or is even aware of it, but his campaign could very easily use Romney 2006 donation against him, just like Romney is using Santorum’s 2008 endorsement to take down his main rival.

Here’s the Romney video, called “Our Favorite.”