If McCain wants to really undermine Romney, he should announce tomorrow that the former Governor of Massachusetts is on a “very short list to be my Treasury Secretary.”  In a single stroke he would show his capacity to extend an olive branch to Romney’s conservative cheerleaders and remind people that Romney is not yet ready for the top job. It wouldn’t be an entirely cynical move.  For years, presidents have turned to grey-haired (or bald) Wall Street sages to “reassure the markets.”  But in today’s economy, more dependent on global trade and private pools of wealth, Romney at Treasury makes a lot more sense. It would also be the first step to start to unite the party, despite what  anti-McCain fanatics think.