CINCINNATI — President Barack Obama and his Democratic allies aren't waiting for Republican Mitt Romney to reveal his vice presidential choice. They're already trying to scuff up those considered by political insiders to be most likely to join the GOP ticket.

The president's campaign started swinging at the potential Republican running mates this week while urging home-state Democrats to chime in about the shortcomings that — as emails to donors and supporters put it — "Americans need to know." The pre-emptive strikes are an effort to define a possible No. 2 in a negative light and reflect a sense that time is precious to sway opinion in a stubbornly close presidential race dashing quickly toward November.

Tim Pawlenty? The former Minnesota governor is a fee-raiser whose record "is painful for the middle-class families who lived under his leadership," the Obama campaign argues.