Former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE defended his policies against more progressive ideas in an interview that aired on Friday, saying mainstream Democrats have won most general election races.

"Look who won last time out," Biden told CNN's Chris Cuomo Chris CuomoCNN's Don Lemon: 'Blow up the entire system' remark taken out of context CNN's Lemon: 'We're going to have to blow up the entire system' if Democrats win back White House, Senate Giuliani criticizes NYC leadership: 'They're killing this city' MORE. "In the general election fights, who won? Mainstream Democrats who were very progressive on social issues, and very strong on education, health care."

Biden: “I think Ocasio-Cortez is a brilliant, bright woman, but she won a primary. In the general election fights, who won? Mainstream Democrats who are very progressive on social issues and very strong on education and healthcare” https://t.co/sZsGVNIduV pic.twitter.com/fcjaAtFEV2 — CNN Politics (@CNNPolitics) July 5, 2019

A number of progressives, including Rep. Alexandria Ocasio-Cortez Alexandria Ocasio-CortezOn The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline McCarthy says there will be a peaceful transition if Biden wins Anxious Democrats amp up pressure for vote on COVID-19 aid MORE (D-N.Y.), stormed Congress earlier this year after surprise primary victories against more establishment members of the party, including Ocasio-Cortez's primary opponent, Rep. Joe Crowley Joseph (Joe) CrowleyHillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections 'Markeyverse' of online fans helps take down a Kennedy The Hill's Campaign Report: Trump visits Kenosha | Primary day in Massachusetts | GOP eyes Minnesota as a battleground MORE (D-N.Y.).

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Biden appeared to issue a warning against leftward movement within the party, questioning whether progressives could perform well in a nationwide, general election.

"I think Ocasio-Cortez is a brilliant, bright woman, but she won a primary," he said.

Ocasio-Cortez, for her part, has hit at Biden's centrist stances, warning he will depress turnout in a general election against President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE.

"I think that he's not a pragmatic choice," the rising Democratic star said last month. "If you pick the perfect candidate like Joe Biden to win that guy in the diner, the cost will make you lose because you will depress turnout as well."

“And that’s exactly what happened to 2016. We picked the logically fitting candidate, but that candidate did not inspire the turnout that we needed," she said.

Biden is facing progressive Sens. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.) and Elizabeth Warren Elizabeth WarrenHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Democratic senators ask inspector general to investigate IRS use of location tracking service MORE (D-Mass.) in the Democratic primary, both of whom have proposed leftward-leaning ideas like “Medicare for all.”

The former vice president has warned against those ideas, instead, pointing to his own ideas, which he says are more "rational."

"I have a plan how to do that that's rational, that will cost a hell of a lot less and that will work," he said.