Update (3:22 p.m. EST): DeWine, as expected, endorses Santorum. DeWine says "To be frank, I've had some sleepless nights.  I could not, in good conscience, be on record endorsing Governor Romney when I knew in my heart that Rick Santorum was the better candidate." Keeping with Santorum's anti-negative ads meme, the Ohio attorney general says, "To be elected President, you have to do more than tear down your opponents." In a real zinger, DeWine said Romney has an "astounding inability to provide voters with a rationale to support him." Also: Santorum "is human."

Back in October, DeWine said "I stand with Mitt Romney." He seemed to think Romney could do more than tear down his opponents in the fall. "s a businessman, Mitt Romney understands what it takes to create and maintain jobs. He will fight government bureaucracy, streamline the federal tax code, roll back any unneeded regulation, and do everything in his power to ensure that America is as jobs friendly as possible," DeWine wrote.

DeWine and Santorum have a lot in common: They're both Catholics with big families, they're both from the Rust Belt, and they both got destroyed in their 2006 Senate races. Santorum lost his seat by 18 percentage points; DeWine lost his by 12.

Update (12:35 p.m. EST): It's pretty clear at this point that the main rumor is that DeWine is going to drop his support for Mitt Romney and come over to Santorum's side, which CNN's Peter Hamby tweeted citing "two Ohio sources" confirming.

Update (12:25 p.m. EST): Washington Post reporter Dan Balz supports the DeWine theory with some new background info from a GOP source. He tweets: "Knowledgeable GOP strategist confirms that Ohio AG Mike DeWine, previously with Romney, will endorse Santorum today."

Original: Rick Santorum's flogging a "major campaign announcement" at 2 p.m. Friday in Columbus, Ohio, which apparently involves some high-profile new campaign supporter. But who? Buzzfeed's Rosie Gray got a Santorum source to say a "top Ohio supporter" of Romney would switch sides and back Santorum, and she zeroed in on Attorney General Mike DeWine, whose spokeswoman wouldn't confirm or deny the rumor, nor would she say what DeWine had planned at 2 p.m. But ABC reporter Shushannah Walshe tweets that it may be someone even bigger (if you assume the governor is "bigger" than the AG): "Santorum campaign says today's announcement is 'major.' I asked if it was OH gov John Kasich + they responded, 'It's bigger than Kasich.' " Meanwhile, The Hill's Daniel Strauss tweets that a Santorum spokesperson narrowed the field a little by confirming that the new backer wasn't an Ohio legislator. Which of course, the attorney general and governor aren't.