RICHMOND, Va. (AP) -- With a once-comfortable lead in Virginia now in doubt, President Barack Obama has made a plaintive and urgent appeal to thousands of supporters not to give up on his quest for a second term while renewing his harangues of Republican Mitt Romney.

His voice reduced to a hoarse shout in the midst of a two-day, all-out blitz of Virginia and five other swing states, the president Thursday portrayed Romney as a pandering shape-shifter, molding his message to polls and political expedience.

Obama's 20-minute rallying cry roused about 15,000 people who had waited up to six hours shoulder-to-shoulder under a blazing sun in a suburban park.

In Virginia, polls show Obama and Romney in a close race. A month ago, those same polls showed the president building a lead over Romney.