After House Speaker Nancy Pelosi had rallied her caucus to vote for more funding to deal with the border crisis in June, moderates mocked the inability of radical Democrats to muster more than four votes in opposition. But that vote was a poor measure of the influence of the leftist quartet.

Moderate Democrats reassure themselves that the so-called “Squad” — Reps. Alexandria Ocasio-Cortez, Ilhan Omar, Rashida Tlaib and Ayanna Pressley — are fringe figures whose reputation has been exaggerated, mostly ­owing to their clever use of social media and GOP attacks.

But the notion that AOC and her allies are political ciphers is a myth that is being debunked on a daily basis. Far from being marginalized, the Squad is dictating the party’s agenda. More than that, it’s painfully obvious that Pelosi and fellow party leaders fear the Squad.

That was made clear last week, when Pelosi and AOC met and emerged arm-in-arm to declare their dedication to party unity. Earlier, AOC had all but accused Pelosi of racism, the sort of insult that would have resulted in any other freshman member being severely punished by a speaker well-known for holding grudges.

But instead of being compelled to bend the knee, AOC was treated as an equal.

The speaker may secretly share President Trump’s wish that the Squad should be making trouble in some other country’s legislature. And Pelosi may well regard with horror the Squad’s willingness to threaten establishment Democrats; AOC thumped party crony Joe Crowley in 2018.

But the Democratic base has now embraced the four as ­heroines of the #Resistance to Trump, rendering them not only invulnerable to Pelosi’s disciplinary authority but giving them power they have only ­begun to exercise.

That’s why many of the radical ideas that they have championed and their spirit of contempt for compromise have taken the left by storm.

How else to explain why a top-tier Democratic presidential candidate like Sen. Kamala Harris would seek out AOC as a partner on her environmental platform?

In a different political universe, someone like AOC would be courting a figure like Harris for favors. Instead, it’s Harris who desperately wants the freshman New York lawmaker’s seal of approval.

Though AOC hasn’t deigned to endorse Harris (she worked for Bernie Sanders in 2016), the pair rolled out a new bill this week in the midst of the senator’s preparations for the next Democratic debate.

The bill ostensibly aims to ­ensure that low-income Americans will somehow benefit from AOC’s fantastical Green New Deal. But the real point was for Harris to associate herself with the Squad’s agenda.

House Judiciary Committee Chairman Jerry Nadler’s kowtowing to the Squad offers even more direct evidence of the four radicals’ power to terrorize the party mainstream.

The Manhattan Democrat, who presided over last week’s disastrous Robert Mueller hearing, normally follows Pelosi’s lead. But he is defying the speaker by signaling that he will push for impeachment, even though most Democrats know this is political poison for their 2020 hopes — not to mention pointless.

Nadler may enjoy the attention this has given him, but the real reason he is still pushing ­impeachment talk is to forestall a left-wing primary challenge against him next year. The congressman already has a credible left-wing primary opponent in Lindsey Boylan, a former Gov. Andrew Cuomo aide who has raised enough money to mount a serious challenge.

Nadler is desperate not to ­allow any room to his left on ­impeachment. Avoiding Crowley’s fate consumes his whole political being. He knows that if he slow-walks impeachment, he will become a piñata for the left and stand a fair chance of losing the seat he has held for nearly three decades.

Democrats like Nadler are running scared and ignoring the long-term political consequences for the party of echoing the radicals’ rhetoric. The same explanation applies to the willingness of the party’s presidential candidates to endorse ­open borders and free health care for illegal immigrants.

The Squad may be few in number, but its members’ ability to intimidate party veterans demonstrates that Trump isn’t wrong to speak of them as the true face of the Democratic Party.

Jonathan S. Tobin is editor in chief of JNS.org and a contributor to National Review.

Twitter: @JonathanS_Tobin