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Rick Santorum has weighed in on the fierce primary battle in the Indiana senate race. The former presidential candidate tweeted his support of State Treasurer Richard Mourdock over longtime Sen. Dick Lugar.

@RickSantorum: I encourage Hoosiers to help GOTV for @RichardMourdock. If I lived in Indiana he'd have my vote in Tuesday's #INSen race.

Lugar has held the seat since 1976, but Tea Party favorite Richard Mourdock is waging a serious challenge and is leading in state polls.

Mourdock also has the backing of anti-tax stalwart Grover Norquist, former Alaska Gov. Sarah Palin, and Minnesota Rep. Michele Bachmann. Lugar is endorsed by Arizona Sen. John McCain and Indiana Gov. Mitch Daniels.

Unlike his support of John Bruning in the Nebraska senate race, which Santorum announced via press release Thursday, his backing of Mourdock was a much more under the radar affair with just the tweet of support.

Santorum has said campaigning for and supporting conservatives in House and Senate races will be part of his next venture since leaving the GOP presidential primary.

Santorum sent an email to supporters Friday saying he will be making an "exciting announcement about what I will be doing next…but before I can make this announcement, I need to spend some time erasing my remaining campaign debt."

The email asked supporters to donate in order to erase the debt.