ABC News is reporting that Marco Rubio may no longer be the front-runner for Mitt Romney's running mate as the GOP pick for vice-presidential candidate.  The network now says that Tim Pawlenty may have taken the lead in that horse race.

The network quotes campaign sources as saying that Pawlenty has become their most effective surrogate for the candidate on the stump...and they say that Pawlenty enjoys a positive relationship with the Republican presidential candidate, as well.