Santorum expected to move closer to 2012 bid

Former Sen. Rick Santorum (R-Pa.) appears poised to move a step closer to an official 2012 presidential campaign Wednesday night.

The former senator is expected to make a "big announcement" during an interview with Fox News's Greta Van Susteren and could reveal the formation of a presidential exploratory committee.

Santorum has already publicly committed to two early presidential debates, but to participate in a May 5 debate in South Carolina, candidates must have officially formed exploratory committees or formally declared a presidential candidacy.

Should Santorum take that step Wednesday, he would be the fifth GOP hopeful to formally file paperwork for an exploratory committee. Former Minnesota Gov. Tim Pawlenty, former Massachusetts Gov. Mitt Romney, former Louisiana Gov. Buddy Roemer and conservative talk host Herman Cain all have official committees.  

Santorum, meanwhile, is headed back to New Hampshire on Thursday for a three-day swing through the state that includes a Friday rally with Tea Party activists on the steps of the state capitol in Concord.