Attacking Romney on leadership will bear a lot more fruit than just attacking him on the policy alone (or lack thereof, to be precise). Because leadership is a quality that all voters consider when making up their minds -- not just one or two demographics.
With Mitt Romney virtually certain to win the Republican nomination, speculation is already turning to his choice of a running mate. Sen. Marco Rubio (R-FL) seems to be at or near the top of almost everybody's list. But I would strongly caution Mr. Romney against picking the freshman senator.