The Democratic Party’s highly choreographed effort to show unity at its national convention this week experienced a brief interlude Tuesday night when one of the party’s most prominent liberal stars took the virtual stage — though only for a minute.

Rep. Alexandria Ocasio-Cortez’s move to nominate Sen. Bernie Sanders (I-Vt.) for president was entirely symbolic as the party rallies around nominee Joe Biden to challenge President Trump. But while the party gave the freshman congresswoman only one minute to speak, her message was a reminder to a potential President Biden: that the far-left is a force he will have to reckon with should he win in November.

“In a time when millions of people in the United States are looking for deep systemic solutions to our crises of mass evictions, unemployment and lack of health care . . . and out of a love for all people, I hereby second the nomination of Senator Bernard Sanders of Vermont for president of the United States of America,” she said.

On Aug. 18, the second night of the virtual Democratic National Convention, delegates named Joe Biden the presidential nominee of their party. (The Washington Post)

While the address was diplomatic, the New York Democrat — who did not mention Biden once — has been working with liberal groups to oust centrists like Biden in hopes of strengthening liberals’ foothold in Congress next year. And they’re already poised to increase their numbers, expanding their clout as they seek to push the House — and the next Democratic president — into embracing policies such as Medicare-for-all and the Green New Deal.

“Right now what you’re seeing is that we’ve got a common goal to beat Donald Trump, but come January, we maybe have a different goal,” said Corbin Trent, a former Ocasio-Cortez aide and political adviser. “They won the nomination, so they get to pick the game plan. Now, that doesn’t mean that they get to pick the game plan in the midterms, when we start primarying their a--es. And it don’t mean that they get to pick the game plan when we start recruiting for 2024 and we primary their a--es.”

The moment comes as the party led by pragmatic-minded septuagenarians and octogenarians — Biden is 77 and House Speaker Nancy Pelosi (D-Calif.) is 80 — has sought to feature a more ideologically diverse crop of rising stars. On Tuesday, 17 Democrats delivered the keynote address at the convention; all are under 50.

Those included liberal leaders such as Stacey Abrams, the Black former Georgia House minority leader who nearly defeated Gov. Brian Kemp (R), as well as moderate Rep. Conor Lamb (D-Pa.), who flipped a Trump district in western Pennsylvania in a 2018 special election.

The selection of fresh, young faces underscores the racial and ideological diversity that Democrats hope will deliver them the Senate and the White House, as it did the House in the 2018 midterms. Liberals, however, are already thinking ahead to January, when they hope to force a potential President Biden and Pelosi into advancing some of their prized proposals.

“We have to be leveraging our membership in a way that will get concessions from a Biden White House on issues like criminal justice reform and health care,” said Mondaire Jones, who won the primary in New York’s 17th Congressional District and is expected to win on Election Day due to the left-leaning tilt of his district. He cited Medicare-for-all.

Throughout the primary season, Biden owned the centrist lane for Democrats, beating back the far-left’s calls for universal health care and free college and refusing to join many in the party in endorsing the Green New Deal — yet still finding a way to secure the nomination.

Down ballot, however, liberal outside groups were highly successful in lifting their candidates to primary wins over establishment Democrats. Earlier this month, Cori Bush, the 44-year-old Black Lives Matter activist, unseated 10-term Rep. William Lacy Clay, the 64-year-old heir to a St. Louis political dynasty. Before her, Jamaal Bowman, a 44-year-old former middle school principal, took down 16-term Rep. Eliot L. Engel (D-N.Y.), the chairman of the House Foreign Affairs Committee. Both are expected to win in November in strongly Democratic districts.

All told, Justice Democrats, the group that launched Ocasio-Cortez’s candidacy just over two years ago, has won five of the nine primaries it has participated in during this election cycle. And since Trump became president, the far-left has managed to unseat five establishment Democrats, a warning to the broader party.

It’s unclear how effective the crop of newcomers will be in Congress. Much ink has been spilled over the past two years likening Ocasio-Cortez and her “Squad” of three liberal freshmen to the House Freedom Caucus, a band of tea party candidates who regularly ran roughshod over GOP leaders but had little legislative success.

Few congressional liberals beyond that quartet were willing to band together to play hardball with Pelosi, though the Progressive Caucus has been able to secure some wins on internal border security measures and prescription drug proposals. However, on the left’s demands on health care and climate change, Pelosi has routinely sidelined their priorities for fear that they would repel swing voters around the nation and endanger the 31 Democrats representing districts Trump won in 2016.

Activists who have helped elect the new group of liberals are already saying next year will be different, as their numbers allow them to fight in a way they could not in this Congress.

“They’re more powerful and willing to flex their muscle. . . . There will definitely not be a honeymoon period for Joe Biden,” said Waleed Shahid, a spokesman for Justice Democrats. “Increasingly the progressive caucus and the Squad will get better at organizing to pass legislation and improve legislation that the party leadership is pushing.”

While they’ve been unable to secure many legislative victories in Congress so far, Ocasio-Cortez’s wing of the party has already shown its ability to transform the broader Democratic platform. Most Democrats running for president embraced its liberal policies. And more recently, even Biden has added a mention of the Green New Deal to his policy platform for climate change.

“Biden believes the Green New Deal is a crucial framework for meeting the climate challenges we face,” his website reads, nodding to Ocasio-Cortez’s proposal.

Ocasio-Cortez, notably, has also joined Biden’s climate change task force in a show of unity — however temporary.

In a sign of the tensions simmering behind the scenes at the convention, some left-wing activists on Tuesday organized a ­#LetAOCSpeak campaign, with a petition circulated by the Young Delegates Coalition asking the DNC to give her more time. AOC, as she’s sometimes called by her initials, was given only one minute to speak.

“We call on you to have Rep. Alexandria Ocasio-Cortez give the keynote address at the Democratic National Convention or, at minimum, have as much time to speak as is given to Republican John Kasich. AOC is one of the Democratic Party leaders who is most respected by young Democrats and progressives,” the petition read.

Jones said it was unfortunate that the DNC didn’t give her more time.

“She is easily one of the most important voices in American politics today, and a leader in the progressive movement, and I think it’s shameful that she was not given significantly more time, whereas half of the Republican Party appears to have been allotted keynote slots,” he said.

The agenda of the far-left has, in many ways, been leadership’s worst nightmare. Pelosi, while a former liberal activist herself, has long maintained that the party needs a big-tent approach that enables moderates to represent their districts and reach out to conservatives. That’s one of the reasons Medicare-for-all has gotten hearings but no votes in the House.

But increasingly, more Democrats are supporting these proposals on their own.

Liberal Ritchie Torres, who won a crowded primary in New York’s 15th Congressional District and is expected to be elected in November, said he doesn’t think it will take aggressive tactics to get Biden to support ideas like Medicare-for-all once he is elected. The conventional wisdom of the far-left being a “thorn in the side” of the party, he argued, has changed because the party itself is moving in that direction already, and leaders will have to follow.

“The Democratic Party is far more progressive now than it was 20 years ago or even 10 years ago,” he said. “The progressive renaissance in America . . . has expanded the realm of what can be achieved politically. . . . I think the left has given a future Democratic president greater freedom to govern with . . . policy ambition.”

David Weigel in Milwaukee contributed to this report.