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.
Clinton also said at the fundraiser that Republicans and Romney have adopted Europe's economic policies. "Who would have ever thought that the Republicans who made a living for decades deriding Old Europe would embrace their economic policies," he said.
For his part, Obama said the economy had been difficult for so many voters that some could reach the point that "you're willing to try just about anything, even if you've seen it before."
Clinton's larger point in the interview last week was that Obama is the better choice to steer the economy, and the White House denied that Clinton "made news." The televised remark nonetheless gave Republicans campaign gold just as the government released a disappointing report saying the United States created far fewer new jobs in May than expected -- a big political blow for Obama.
Obama and Clinton also are on opposite sides of a close Democratic congressional primary contest in New Jersey. Clinton also campaigned last week for Wisconsin Democratic gubernatorial candidate Tom Barrett. Barrett faces Republican Gov. Scott Walker in a special recall election contest on Tuesday but has seen little backing from the Democratic Party or Obama.
Romney's campaign sought to exploit the differences, circulating Clinton's comments from a December 2007 interview on PBS in which he suggested that electing Obama would carry some risks. "When is the last time we elected a president based on one year of service in the Senate before he started running?" Clinton said.
Still, Clinton's ability to deliver campaign dollars and his record as a sound campaign strategist make him an asset to the Obama campaign that apparently outweighs any drawbacks. For Clinton, Obama is not only the head of their shared party, he may be the best entree for a second Clinton administration if Hillary Clinton were to run for president in 2016.
The two appeared together at a fundraiser in April and plan several more joint events across the country. Clinton has also recorded a video for Obama and sent campaign emails to supporters.
Obama campaign bundler and billionaire investor Marc Lasry held an exclusive reception Monday night, followed by a gala at the Waldorf-Astoria hotel, where rocker Jon Bon Jovi closed a dinner concert with the upbeat Beatles anthem "Here Comes the Sun."
Taking the stage a short while later, Clinton harkened back to the better economic days of his presidency.
"Remember me? I'm the guy who gave you four surplus budgets out of the eight I sent" to Congress, he said to applause.
Clinton and Obama were focusing their message Monday on economic opportunity. Polls show that economic trends are likely to determine the election, a development that could help Romney if the economy sags significantly. Obama and Romney were tied at 46 percent in Gallup polling last week of national election preferences.
"They've got a nominee who is expressing support for an agenda that would reverse the progress we made and take us back to the exact same policies that got us into this process in the first place," Obama said, although he complimented Romney by name for his success in business.
The evening concluded with an event dubbed "Barack on Broadway" at the New Amsterdam Theatre. Obama will return to Manhattan next week for a fundraiser at the home of "Sex and the City" actress Sarah Jessica Parker.
While Obama was in New York, Romney was on the West Coast to attend fundraisers in Portland, Ore., and Seattle.
Obama's campaign released a video of campaign manager Jim Messina urging supporters to "stay focused, work hard and ignore the ups and downs." The campaign included a map listing eight undecided states: Colorado, Iowa, Wisconsin, Ohio, Virginia, North Carolina, New Hampshire and Florida.
Lasry, head of the hedge fund Avenue Capital, told CNBC last week that private capital investment as practiced by Bain Capital can do worthwhile things. He shrugged off as "politics" Obama's recent references to investment choices he claims have ravaged jobs for the sake of investors' profits.
About 50 people attended the $40,000-per-ticket reception at Lasry's home, an art-filled townhouse on Manhattan's tony Upper East Side. Tickets to the 500-person gala at the Waldorf began at $2,500. Those who contributed $35,800 or raised $100,000 gained access to a smaller reception with Obama.
The concert at the New Amsterdam Theatre drew 1,700 people. Tickets for that event started at $250, the Obama campaign said.