When will mainstream Democrats start fighting back? When will they stop playing nice with a left fringe that regards them, not Republicans, as the opposition, if not the enemy?

Rep. Alexandria Ocasio-Cortez's threat to kill President Joe Biden's hard-fought infrastructure deal should have been a last straw.

"Good luck tanking your own party's investment on childcare, climate action, and infrastructure while presuming you'll survive a 3 vote House margin," the New York Democrat blustered. "Especially after choosing to exclude members of color from negotiations."

The great irony in this racial game-playing is that Ocasio-Cortez and her allies in the Democratic Socialists of America work tirelessly to destroy the careers of powerful Black and Hispanic political leaders who disobey their orders.

Early in her career, Ocasio-Cortez reportedly weighed backing a primary challenge against Hakeem Jeffries, a Black congressman representing parts of Brooklyn and Queens. High in the Democratic House leadership, Jeffries would be deemed a "progressive" by any set of standards other than those of the Democratic Socialists of America.

In 2020, an Ocasio-Cortez staffer tried to knock off Rep. Gregory Meeks, the Queens party boss who is also Black. Meeks survived the challenge.

Eric Adams, a Black former police officer, now the Democratic nominee for New York City mayor, has come under fire from the Twitter-fueled left. "I'm no longer running against candidates," he said recently. "I'm running against a movement. All across the country, the DSA socialists are mobilizing to stop Eric Adams."

During the mayoral primary, Ocasio-Cortez endorsed activist Maya Wiley. When New York Democrats' votes were counted, Wiley placed third. Adams triumphed with big support from the Bronx and other working-class communities of color.

In the recent Ohio special election to replace Rep. Marcia Fudge, the far left championed Nina Turner, who famously likened a vote for Biden to eating a "bowl of s—-." A Turner supporter, the rapper Killer Mike, called House Majority Whip James Clyburn, the civil rights icon, "incredibly stupid" for having endorsed Biden in last year's presidential primaries.

None of these vicious but also idiotic attacks on fellow Democrats cost Turner the support of Ocasio-Cortez, her "Squad," or Vermont Sen. Bernie Sanders. But Democratic voters apparently thought differently. Turner went on to lose the primary despite having outraised moderate opponent Shontel Brown by $3.2 million.

Meanwhile, ask Google for pictures of Democratic Socialists of America meetings. They show a sea of mostly white lefty "thinkers" who believe they know better than people of color about what people of color need. Some people call this mindset "white saviorism." Ocasio-Cortez's strongest support comes from professionals now gentrifying neighborhoods in Queens.

After Turner's loss in Ohio, Jeffries let loose his frustrations. "The extreme left," he said, "is obsessed with talking trash about mainstream Democrats on Twitter, when the majority of the electorate constitute mainstream Democrats at the polls."

And right he is. A command of social media magnifies the left's importance while actual votes by Democrats usually show it to be a fringe, not the fabric, of the party. Moderate Democrats recently beat out its candidates in New York, Virginia, Louisiana, and, as noted, Ohio.

Ocasio-Cortez's glamor-puss passion for celebrity is irritating, but that's not the larger concern for Democrats. It is that she and other radicals are serving the interests of Republicans and don't seem to care.

The left wing cost Democrats House seats in 2020 and has become a major worry for the 2022 midterms. The Republicans need to win only a handful of purple districts to take control of the House.

So, hasn't the time come for mainstream Democrats to find good progressives to primary some of the more destructive far-left candidates? They could start with Ocasio-Cortez, who herself has proven that upsets can happen.

Follow Froma Harrop on Twitter @FromaHarrop. She can be reached at fharrop@gmail.com. To find out more about Froma Harrop and read features by other Creators writers and cartoonists, visit the Creators webpage at www.creators.com.