Former Vice President Joe Biden, in an interview aired Friday, took a swing at the far-left wing of the Democratic Party, warning that the majority of Democrats are not “way left” and that moderate Democrats are more electable in general elections.

In an interview with CNN in Iowa, the 2020 Democratic presidential hopeful pointed to the 2018 midterms, where a number of center-left Democrats won close races.

"That's what this election is about. I'm happy to debate that issue and all those issues with my friends because guess what, look who won the races. Look who won last time out," Biden said.

He mentioned Rep. Alexandria Ocasio-Cortez, D-N.Y., who beat longtime Rep. Joe Crowley in a shock primary win, before cruising to a general election victory in a comfortably blue district. She is now one of the key figures in the party’s progressive wing.

Biden called her “bright” but cast doubts on how well such a left-wing figure would do in a national general election.

"By the way, I think Ocasio-Cortez is a brilliant, bright woman, but she won a primary. In the general election fights, who won?” he asked. “Mainstream Democrats who are very progressive on social issues and very strong on education and health care."

“My north star is the middle class, when the middle class does well, everyone does well,” he added.

Biden is leading the 2020 field in polling but faces pressure over his more moderate positions from the most left-wing field ever of Democratic candidates. Candidates have embraced decriminalizing border crossings, slavery reparations, higher tax rates, free college and a Green New Deal.

In that shift leftward by the party, Biden has faced criticism for past positions he held in the Senate, and has himself shifted to the left somewhat, including saying that he supports health care for illegal immigrants. Biden, though, said Friday that he does not support decriminalizing illegal border crossings, after giving an unclear stance on the matter at last week's debate.

The interview comes as Biden is fighting to keep his momentum on the heels of that debate. On the stage in Miami, Biden was challenged by Sen. Kamala Harris, D-Calif., on his opposition to busing in the 1970s -- a clash that has since hurt Biden and boosted Harris in the polls.

Harris, while campaigning in Iowa on Thursday, knocked Biden’s preparation for that debate.

“You know, if he and his team weren’t prepared for the topic, I don’t know what to say about that,” she said.

In the interview with CNN, Biden acknowledged he wasn’t prepared for her attacks.

"I was prepared for them to come after me, but I wasn't prepared for the person coming at me the way she came at me," Biden said, adding that she knows him and also knew his son Beau Biden -- who passed away in 2015.

He also defended his performance in the debate, saying he didn’t want to get involved in the “scrum."

“Do you think the American public looked at that debate -- take me out of it -- and thought ‘Boy I really like the way that’s being conducted, they’re really showing themselves to do really well’?” he asked. “Come on, man.”

Fox News' Peter Doocy contributed to this report.