As Republicans released a TV ad hitting Sen. Michael Bennet (D-Colo.)  for supporting the stimulus bill, he defended his vote during a roundtable with reporters Thursday.

"I think passing the recovery package was an essential thing to do in order to save us from, you know, the Great Depression," he said. "And I think economists on both sides of the aisle say it was roughly responsible for three points of GDP."

The National Republican Senatorial Committee released its second ad of the campaign Thursday, which targets Bennet's vote on the stimulus package.

"He voted for the stimulus bill, promising us jobs," a female announcer says in the ad. "But unemployment’s up."

"It's amazing if you look at the advertising that's being run against me," Bennet said at an event hosted by the Third Way, a Democratic-leaning Washington think tank. 

"I think the recovery package saved us from falling into not just the worst recession since the Great Depression, but another Great Depression," he said. "But that's not saying a lot from the vantage point of our kids. That seems to me to be not a sufficient standard for success or progress, and that's the point I was trying to make."

Bennet's facing Weld County District Attorney Ken Buck (R) in November. Buck clinched the Senate nomination with the support of the Tea Party and other grassroots conservative groups. Democrats have sought to label Buck and other so-called Tea Party candidates as too "extreme."

Bennet made the same argument.  

"I think [Buck is] very extreme on a number of issues from Colorado's point of view,” he said. "He's argued for the privatization of Social Security. He's argued for an end to the Department of Education, an end to federal student loans. He's pro-life, and with no exceptions for rape or incest. He supports Paul Ryan’s [budget] blueprint. Those are positions that are extreme and out of step with the people of my state."

Despite holding views that Bennet argues are "extreme" for Colorado, the senator said he doesn't expect to have an easy race against Buck. "The polls are going to stay close to the end for all kinds of reasons," he told The Ballot Box.

Asked if he would call on President Obama for help in the general election, Bennet was noncommittal. 

"I'm grateful for his support," said Bennet, who got fundraising help from the president during his primary. "We're looking at this day by day by day. I mean, all these questions."