Chuck Hagel spent nearly eight hours in the hot seat Thursday in a bruising confirmation hearing for President Obama's nominee for secretary of defense.

Hagel is a Vietnam veteran and a former GOP senator, but it's his former Republican colleagues who are the most critical of his nomination.

One of his most outspoken critics, fellow Vietnam War veteran Sen. John McCain, R-Ariz., questioned Hagel's stance on the 2007 Iraq surge.

"Were you correct or incorrect when you said that the surge would be the most dangerous foreign policy blunder in this country since Vietnam?" McCain pressed the former Nebraska senator at Thursday's hearing.

"Well, I'm not going to give you a 'yes' or 'no' answer on a lot of things," Hagel replied.

"Well, let the record show that you refused to answer that question," McCain said.

Republicans cite "fundamental disagreements" with Hagel's judgment and worldview on key issues, like nuclear weapons, terrorism, and Iran.

Hagel also faced critics who claimed he is anti-Israel, specifically addressing a past comment about what he called the "Jewish lobby."

"I've already said I regret referencing the 'Jewish lobby,' Hagel said. "I should have said 'pro-Israel lobby.' I think it's the only time on the record that I've ever said that."

Hagel urged lawmakers not to write him off based on several controversial votes and quotes from his entire career in the Senate.

"No one individual vote, no one individual quote, no one individual statement defines me," he told lawmakers.

If confirmed Hagel will be the first secretary of defense to have seen combat as an enlisted soldier.

"I don't see the lens of every world event and whether we should use American power through the lens of Vietnam. But it's part of me," Hagel said.

In order to lock down the nomination, Hagel needs the support of all Senate Democrats and at least five Republicans. Many Republicans have already said they plan to vote against Hagel.

But experts say it's unlikely enough Democrats would go against the president to prevent Hagel from becoming the next secretary of defense.

Many lawmakers present at the hearing, both Republican and Democrat, say Hagel's performance was not impressive. They said they were shocked at how ill-prepared he seemed for questioning.

A vote on Hagel could come as early as next week.