COLLEGE PARK, MD — Speaking to a pumped up crowd of more than 15,000 at the University of Maryland’s Comcast Center this afternoon, Barack Obama took aim at likely Republican nominee John McCain as the two remaining Democratic candidates continued a fierce battle over who is the most electable in November.

“Senator Clinton says, ‘…I’ve been around a long time, so I can go after the Republicans, and I’m tough,’ Obama said, paraphrasing one of Clinton’s common arguments about why she would be stronger in a general election. “Well, let me tell you something. I may be skinny, but I’m tough too. I’m looking forward to mixing it up with John McCain.”

“I admire Senator McCain’s half a century of service to this country,” Obama said, in what could be construed as an underhanded reminder of McCain’s age. “He is a genuine American hero.”

After all the pleasantries, however, Obama launched into an attack that made McCain out to be a Bush clone.

“He wants to perpetuate the failed Bush economic policies, and continue giving tax breaks to the wealthy while we’re working up a deficit and people’s needs go unmet,” Obama lamented. “He wants to continue a 100 year war in Iraq, spending $9 billion a month that can be spent right here in the United States of America.”

He also said that he would be better able to attract Republicans. “They call them Obamacins,” he joked.

The assault from Obama comes on the same day that Mark Penn, Clinton’s chief strategist, released a memo arguing that Clinton was more formidable against McCain because of her ability to withstand the “GOP attack machine,” her stronger background on national secuirty, and because her negatives “are already factored in,” while Obama’s will rise.