Alexandria Ocasio-Cortez, the young and charismatic Democratic candidate who ousted incumbent and party bigwig Rep. Joe Crowley in a recent New York Primary, is now facing pushback from another major figure in the party's history.

In a Wall Street Journal op-ed posted Tuesday, Joe Lieberman called on Democrats to vote against Ocasio-Cortez.

Lieberman, the former independent senator from Connecticut who also ran as Al Gore's vice presidential running mate in 2000 on the Democratic ticket, encouraged voters to cast their ballots for Crowley, even though Crowley has officially backed out of the race.

Crowley remains a potential contender because he will be listed on the Working Families Party ticket in November 2018 due to the quirks of New York election law. The same candidate is often nominated by different parties in the race, and the Working Families Party endorsed Crowley prior to the Democratic primary. Now with Ocasio-Cortez as the Democratic nominee, the WFP would like to nominate her — but they can't remove Crowley without his consent.

And Crowley has refused to jump through the legal hoops New York would force him to comply with if he were to pull out.

Lieberman, who was always on the right-leaning side of the Democratic Party (he was nearly John McCain's running mate in 2008), has apparently been spooked by Ocasio-Cortez's progressive politics. So he's urging voters to cast their ballots for Crowley on the WFP ticket — even though Crowley has already conceded to and endorsed Ocasio-Cortez.

Along with predicting the usual doom and gloom of national bankruptcy and higher taxes as the result of Ocasio-Cortez's progressive policies, Lieberman also denounces her positions on Israel, Syria, and abolishing ICE — a view he completely misrepresents as advocating that no immigration or customs rules be enforced.

But he also warns that Republicans are calling Ocasio-Cortez the "new face" of the Democratic Party.

"[House Minority Leader Nancy Pelosi] knows that if Democrats are to regain a majority, it will be by winning swing districts with sensible, mainstream candidates," Lieberman writes. "Ms. Ocasio-Cortez is making that task harder across America."

Democrats and progressives are always told that their aims need to be moderated to be successful, even as the Republican Party becomes increasingly extreme on a range of issues. And at the same time, Lieberman doesn't even consider how discouraging and demoralizing it might be for Democratic voters to see a potential rising star undermined by the party's leadership after she won a primary fair and square.

Lieberman was one of the main advocates against a public option during the 2009 health care debates. The omission of a public option from Obamacare, many now believe, was both bad policy and politically shortsighted. Again, Lieberman appears to be making the same mistake.

He's needlessly embracing knee-jerk opposition to progressive politics and diminishing himself and the whole Democratic Party in turn.

Correction: This story originally misstated when Liberman ran for vice president.