CINCINNATI (AP) - President Barack Obama and his Democratic allies aren't waiting for Republican Mitt Romney to reveal his vice presidential choice. They're already scuffing up the likeliest picks.

In emails to donors and supporters, Obama's campaign is critiquing the Republican running mate favorites while urging home-state Democrats to chime in about their shortcomings.

The pre-emptive strikes reflect a sense that time is precious to sway opinion in a close presidential race dashing quickly toward November.

Obama's campaign has targeted New Jersey Gov. Chris Christie, former Minnesota Gov. Tim Pawlenty, Ohio Sen. Rob Portman and Florida Sen. Marco Rubio. Independent groups sympathetic to Obama are also starting to unload their opposition research on the would-be vice presidents.

Romney's campaign criticized Obama for seeking critiques and called them little more than "negative smear campaigns."

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