Barack ObamaBarack Hussein ObamaThe 'Palmetto Promise': South Carolina will decide the race Obama remembers Kobe Bryant in speech to NBA All-Stars: 'Nothing is more heartbreaking' Warren highlights work with Obama, Harry Reid in new Nevada ad MORE is warning supporters that the general election fight between him and John McCainJohn Sidney McCainEleventh Democratic presidential debate to be held in Phoenix Moderate Democrats now in a race against the clock Biden on Graham's push for investigation: 'I don't know what happened' to him MORE may get ugly, but the Illinois senator is vowing not to back down.

"If they bring a knife to the fight, we bring a gun," Obama said at a fundraiser in Philadelphia Friday, according to pool reports.

"We don't have a choice but to win," Obama said, joking that he has heard "folks in Philly like a good brawl. I've seen Eagles games."

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Obama again said that the GOP will make try to make him look "scary" to voters.

Obama pledging to swing back at the GOP drew much applause from the crowd.

Republican National Committee spokesman Alex Conant said Obama's rhetoric abandons Obama's campaign themes of hope and change.

"In the last 24 hours, he