At nearly every stop on the campaign trail, Mitt Romney offers his business resume as the primary reason he believes he's the right man to be president in this economy.

In Dubuque, Iowa, Romney told a group of factory workers about an American brand he helped create.

"I had the fun of getting involved in a startup. It's called Staples," said Romney.  Romney and his team at Bain Capital were largely responsible for Staples, and today the company has 90,000 employees.

But there is now new heat on Romney about the jobs lost at other companies where Romney and his team moved in. They invested in these companies, made them more efficient - at times producing more with fewer workers - and then sold them for a profit.

Newt Gingrich was the first among Republicans to criticize Romney on this: "If Gov.  Romney would like to give back all the money he's earned from bankrupting companies and laying off employees over his years of being, then I would be glad to then listen to him," said Gingrich.

Romney, who is worth an estimated $250 million, has faced previous criticism for his work at Bain. In 1994, Ted Kennedy aired a series of ads with workers at an office supply factory who lost their jobs after Romney's Bain capital took a majority stake.

"You're not creating jobs, you're taking them away.  To line your pocket," said the ad.

Political observers say if Romney is nominated, the same argument could be expected from President Obama.

"I think that will be a central part of the argument. … Do we really want to turn this economy over to the same people that messed it up?" said political consultant Matthew Dowd. "Mitt Romney's argument on that is we're in a global economy, we have to do what's necessary, we have to increase shareholder value, we have to do that and that's the way we can grow out of this."

The founder of Staples, Thomas G. Stemberg, has come to Romney's defense: "After 25 years in business, Mitt Romney understands how jobs come and go, and what we need to do to get our economy back on track."