TAMPA, Fla. (CNN Wire) — Democrats wasted no time on Tuesday trying to undercut Republicans as they began their convention, attacking a key GOP message before party luminaries took the spotlight in Tampa.

Republicans aggressively pushed their convention theme, “We Built It,” while Democrats sought to turn it back on Mitt Romney, who was affirmed as the nominee by a roll call of delegates in the first significant moments of the event.

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Republicans highlighted a remark by President Barack Obama, who said in July that public investment in infrastructure helps businesses grow. “If you are successful, somebody along the line gave you some help. … If you’ve got a business, you didn’t build that,” Obama said at the time.

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Republicans have seized on the comment to suggest that Obama is out of touch with small business owners and does not understand how the private sector works. Democrats, however, contend that their rivals are taking things out of context.

“So as Republicans continue to distort the president’s words and push their ‘We built that’ theme in Tampa,” Los Angeles Mayor Antonio Villaraigosa said from the “war room” Democrats have set up in downtown Tampa near the convention site. “It’s worth asking: What did [Mitt] Romney build?”

Villaraigosa, chair of next week’s Democratic convention in Charlotte, N.C., answered his own question – “A bank account in Switzerland, investments in Bermuda and the Caymans, and an inexplicably large IRA. That’s what he built.”

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Democrats are trying to nail Romney with a one-two punch: casting him as wealthy and privileged and saying that his policies would hurt the middle class.

On Romney’s tenure at the top of Boston private equity firm Bain Capital, Villaraigosa and other Democrats said Bain’s goal when investing in troubled companies was not creating jobs. Instead, they suggested that the firm under Romney destroyed businesses and jobs in order to generate profit for investors.

The Romney campaign quickly fired back.

In an e-mail, Romney spokesman Ryan Williams accused Democrats of launching “false and baseless attacks” against the former Massachusetts governor whose tenure at the firm prior to his public life made him wealthy.

“The facts speak for themselves,” Williams said, “with 23 million Americans struggling for work, nearly one in six Americans living in poverty, and median incomes declining, the Obama campaign cannot defend a record of broken promises and failed policies. Mitt Romney and Paul Ryan have a plan to strengthen the middle class by creating jobs and turning around our economy.”

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