With Obama standing thoughtfully to one side, Clinton slammed Romney by name, an apparent rebuttal to his own comments last week that were widely seen as flattering to Romney's background in business.

Clinton said Obama had earned a second term because of his steering of the economy through a "miserable situation," and that "the alternative would be, in my opinion, calamitous for our country and the world."

Clinton's take came as he helped raise at least $3.6 million for Obama at three New York fundraisers. The two have patched over a personal rift from the 2008 campaign when Obama defeated Hillary Rodham Clinton in a bitter Democratic primary. But Clinton caused some heartburn in Obama's campaign last week by remarking that Romney had a "sterling" business record — an assertion that undercut Democrats' criticism of Romney's decisions at the private equity firm Bain Capital.