Mitt Romney's campaign sought to undermine Bill Clinton's support of President Obama by releasing an ad Thursday in which the former president appears to be calling Obama's economic promises a "fairy tale" during the 2008 campaign.

The 30-second Romney campaign ad, titled "Give Me a Break," was released a day after Clinton fiercely defended Obama's record in his convention speech.

"As the economy gets worse, Barack Obama calls on Bill Clinton to help his failing campaign," the narrator in the ad begins. "He's a good soldier, helping his party's president. But what did Bill Clinton say about Barack Obama in 2008?"

The video then cuts to Bill Clinton campaigning for his wife at a town hall meeting in January 2008. "Give me a break. This whole thing is the biggest fairy tale I've ever seen," Clinton is heard telling an audience.

But the old campaign video in its entirety made no mention of the economy or Obama's campaign promises. Clinton was instead referring to Obama's claim that he was one of the earliest opponents of the Iraq war.

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