Romney talks more on the campaign trail about his business career than his 2003-2007 tenure as governor, when Massachusetts was among the nation's worst for job creation.

"As the governor of Massachusetts, the state ranked 47th out of 50 in job creation and was the third worst in the country for manufacturing jobs," Democratic National Committee spokesman Brad Woodhouse said in a statement today. "In the private sector, Romney benefited by laying people off and shipping jobs overseas. That sort of track record is not going to sit well with the Americans who are looking to find a job with a good wage and decent health care."

Business Career

Romney, who enjoyed front-runner status in the race for the 2012 Republican presidential nomination before Texas Governor Rick Perry entered the contest on Aug. 13, is increasingly pointing to his past role as the head of private equity firm Bain Capital LLC.

The Boston-based firm found profits for Romney, its other executives and its investors, whether the companies they touched boomed, eliminated employees or filed for bankruptcy.

Romney, who spent most of his career at Bain, has assets worth between $190 million and $240 million, according to his financial disclosures.

"I have spent most of my career in the private sector starting new businesses and turning around ailing ones," Romney wrote. "Unlike career politicians who have never met a payroll, I know why jobs come and go."

Obama, 50, may be politically vulnerable amid 9.1 percent unemployment and approval ratings near lows of his presidency.

Election-Day Unemployment Rate

Since World War II, no U.S. president has won re-election with a jobless rate above 6 percent, with the exception of Ronald Reagan, who faced 7.2 percent unemployment on Election Day in 1984 after the rate had dropped more than three percentage points during the previous two years. The median forecast of economists surveyed by Bloomberg puts the rate at 8.6 percent in the third quarter of next year, just prior to the election.

Nevada's unemployment rate was 12.9 percent in July, the highest among the states. Obama won the state in the 2008 election.