Sen. Scott Brown (R., Mass.) has ruled out running for president in 2012. He’d probably back Mitt Romney for the nomination:

Asked if he supported former Republican vice presidential nominee Sarah Palin for president, Brown said he supported Romney. “Well, I’m going to support Governor Romney, and I’m going to see who’s out there in the field and then make my decision,” he told Gangel.
Colin Reed, a Brown spokesman, said Brown had supported Romney before and “will be with him again if he chooses to run.”