Romney’s short list: Rubio, Pawlenty rising, Daniels sliding

Jonathan Karl, Richard Coolidge & Sherisse Pham
Power Players

Spinners and Winners

The search for a Romney running mate is well underway, but whose stock is up, and whose is down?

Sen. Marco Rubio, R-Fla., in the top tier of potential VP nominees, is showing he can play the number one role of a running mate: attack dog. In a blistering speech in South Carolina, Rubio hammered Obama about his "divisive" leadership style, calling it unprecedented in modern American history.

Sliding down the list this week is Gov. Mitch Daniels, R-Ind. Daniels has publicly said he does not want the VP nod but recently he went a step further, saying that he would "disconnect the phone" if he knew that call was coming. Expressing disinterest is good; saying you won't take a call from the party's nominee is not.

Sen. Kelly Ayotte, R-N.H took an entirely different approach. Asked about the prospect of a debate with Joe Biden, she said that it would be "very enjoyable," noting that Biden "has a way with words."

And could this be a tea leaf? The latest Romney television ad features a clip of Romney walking with Tim Pawlenty — making him the first potential running mate to appear in a Romney general election ad. That may or may not mean anything, but Pawlenty has grown close to Romney and won high marks from the Romney team for his work on behalf of the campaign. He is moving up on the list and should now be considered a top tier candidate.

ABC News' Gregory Simmons and Sarah Burke contributed to this report.