NEW YORK (AP) — New York’s congressional candidates have a final chance to make their case Monday on the last full day of campaigning before a primary election in which an ascendant progressive left is taking on establishment Democrats.

The races have become bellwethers of Mayor Zohran Mamdani’s political clout, testing whether the young democratic socialist can leverage excitement he ignited last year to reshape the city’s congressional delegation.

And he has been working hard to promote his slate of three House candidates, lending his star power to several campaign videos, along with hosting a rally with U.S. Sen. Bernie Sanders last week to boost his picks just before the election.

“The party of the past will not be what leads us into the future. We need a Democratic Party with backbone,” Mamdani said.

Meanwhile, in another closely watched race, Jack Schlossberg, the 33-year-old grandson of former President John F. Kennedy, is hoping to ride his family ties and big social media following to a seat in Congress representing part of Manhattan.

But the Kennedy scion is facing strong opposition from Alex Bores, a state Assembly member at the center of a Silicon Valley spending war over his proposals to regulate artificial intelligence, and Micah Lasher, another state Assembly member who has deep experience in New York government and is backed by many of the state’s Democratic leaders. George Conway, an attorney who was once married to a top Trump adviser but later become one of the president’s critics, is also in the race.

In his campaign’s closing stretch, Schlossberg rallied with David Letterman, former host of the “The Late Show with David Letterman.” His mother, Caroline Kennedy, cut a campaign ad for him. Lasher hit the street to meet voters. Bores releasing an ad about the dangers of AI and worked to highlight the millions of dollars that Big Tech players are spending to oppose his run.

Mamdani has not made an endorsement in that race.

Instead, he’s focused on three other congressional contests, including two featuring embattled incumbents.

Darializa Avila Chevalier, a democratic socialist whose campaign has been buoyed by the mayor’s support, is challenging U.S. Rep. Adriano Espaillat, who was the first Dominican American elected to Congress in a district that includes northern Manhattan and part of the Bronx.

Espaillat has drawn attention to inflammatory social media posts Avila Chevalier made in her 20s, attempting to portray her as an unserious candidate. Avila Chevalier, in a recent debate, said she regretted the posts and apologized for one crass post about former Vice President Kamala Harris.

Former city Comptroller Brad Lander got the mayor’s endorsement in his attempt to unseat U.S. Rep. Dan Goldman, a fellow Democrat.

Lander, who appeared in the crowd at a joyous City Hall ceremony celebrating the Knick’s NBA championship win on Thursday, has worked to play up his alliance with the mayor, while Goldman, who did not endorse Mamdani in his mayoral race, has tried to shift the conversation to his own productiveness in Congress.

Mamdani is also supporting Claire Valdez, a former state Assembly colleague and democratic socialist ally, in her bid to defeat Brooklyn Borough President Antonio Reynoso in the race to succeed retiring U.S. Rep. Nydia Velazquez.

Reynoso and Valdez are both progressives who share many similar views, though Valdez has framed herself as a potential Mamdani ally in Washington.

Anthony Izaguirre, The Associated Press