“This past Thursday, January 14, The Cook Political Report moved the open Massachusetts Senate seat rating from Lean Democrat to Toss Up, having moved it from Solid Democrat to Lean Democratic on January 7,” Cook wrote. “We continue to see this race as very much of a Toss Up, with Republican state Sen. Scott Brown holding onto a very narrow, single-digit lead over Democratic state Attorney General Martha Coakley.

“Given the vagaries of voter turnout, particularly in lower participation level special elections, this race could still go either way, but we put a finger on the scale for Brown. Last minute Democratic attacks on Brown have driven his negatives up some and slightly diminished the incredible intensity of support that Brown enjoyed, but it looks more likely than not to hold.”