Just seven months ago, democratic socialist Zohran Mamdani swept to victory in the New York City mayor’s race, becoming the city’s first Muslim leader.

Now, a new slate of candidates is testing the Democratic Party’s political direction in the most populous city in the United States.

New York’s primary on Tuesday will determine which challengers the party nominates to run in the midterm elections in November.

That vote will, in turn, decide which party controls Congress, giving its lawmakers the power to aid or impede US President Donald Trump’s legislative agenda for his final two years in office.

Most congressional districts in New York City are solidly left-wing bastions, meaning the winners of those races are all but assured to skate to victory in November.

But other districts, in places like Long Island and the Hudson Valley, are considered toss-ups. The outcome of those races is expected to play an outsized role in determining who gains a majority in the US House of Representatives.

Here’s what to know:

What time do polls open and close?

Early voting ran from June 13 to June 21. On Tuesday, polls open at 6am (10:00 GMT) and close at 9pm (01:00 GMT on Wednesday).

Israel policy looms large in Lander versus Goldman

Progressive Brad Lander, the former comptroller of New York City, made a pact with Mamdani before last year’s New York City mayoral primary.

The two candidates endorsed each other, urging voters to list them as top picks in the ranked-choice voting system, in an effort to edge out a mutual opponent, former New York State Governor Andrew Cuomo.

The gambit paid off, with Mamdani winning a commanding primary victory over Cuomo. He later sailed to victory in the general election.

Mamdani and Lander’s partnership was an alliance between an avowed anti-Zionist and a self-identified “liberal Zionist”, respectively. But both politicians have advocated for Palestinian human rights in the face of Israeli abuses.

Lander is currently challenging incumbent Congressman Dan Goldman to represent New York’s 10th District, an area spanning lower Manhattan and northern Brooklyn.

But their opposing views on Israeli policy have dominated the Democratic primary. Lander has decried Israeli military action in Gaza, calling it a genocide. He has called Israel’s system of control over the occupied Palestinian territory “apartheid”.

To address the abuses, Lander has called for a ban on US weapons to Israel.

Still, he has argued that Israel has the “right to exist” as a Jewish state and has opposed the boycott, divestment and sanctions (BDS) movement. His track record as comptroller has also come under scrutiny, with pro-Palestine advocates criticising him for investing city pension funds in Israel’s largest defence contractor, Elbit Systems.

Goldman, meanwhile, has emphasised his support for Israel, while heavily criticising the government of Israeli Prime Minister Benjamin Netanyahu. He has maintained that Israel’s war in Gaza does not constitute a genocide and has rejected claims that Israel oversees an apartheid system.

An heir to the Levi Strauss fortune, Goldman has been endorsed by the American Israel Public Affairs Committee (AIPAC), but he has sought to distance himself from the lobbying group, including by returning direct donations.

He has gotten a bump from New York Governor Kathy Hochul and former US House of Representatives Speaker Nancy Pelosi.

Lander, meanwhile, is backed by progressive stalwarts, including Mamdani and US Senator Bernie Sanders. The most recent polls have shown Lander leading Goldman, but margins are expected to be tight in Tuesday’s Democratic primary.

Mamdani-endorsed Democratic socialists

Two primaries will test the electoral power of the Democratic Socialists of America (DSA), a group that leveraged grassroots support to help carry Mamdani to victory last year.

One concerns the race to represent New York’s 13th District, which covers upper Manhattan and the Bronx. There, a surge in support for DSA-endorsed candidate Darializa Avila Chevalier has threatened to upset longtime incumbent Adriano Espaillat, who has held his office since 2017.

The district is diverse, with large Hispanic and Afro-Caribbean populations. It also abuts the district currently represented by Alexandria Ocasio-Cortez, a fellow Democratic Socialist of America member who upset incumbent Joe Crowley in 2018.

But the 71-year-old Espaillat has pushed back against Avila Chevalier’s rise, framing the 32-year-old community organiser as inexperienced and out of step with the Democratic Party.

He has also seized on her past tweets, which include inflammatory statements criticising former US President Joe Biden and 2024 presidential candidate Kamala Harris.

Avila Chevalier has issued a handful of apologies for her online statements, while doubling down on a platform that calls for reform among police, prisons and federal immigration enforcement. She has also vocally supported Palestinian rights.

Espaillat, the first formerly undocumented immigrant elected to the US Congress, has also been a leading critic of the Trump administration’s immigration policies, but he has championed a more incremental approach to reform.

A major flashpoint in the race has been the candidates’ stance towards Israel. Critics, for example, have seized on Avila Chevalier’s attendance at a pro-Palestine protest a day after Hamas attacked southern Israel on October 7, 2023.

Avila Chevalier, however, has said she attended the rally in anticipation of Israel’s response against Palestinian civilians.

Espaillat, by contrast, has won praise from AIPAC. Filings show a super PAC aligned with the powerful lobby has spent hundreds of thousands of dollars to oppose Avila Chevalier.

A leftist battle in Brooklyn and Queens

Covering a section of northern Brooklyn and Queens, New York’s 7th Congressional District has also seen a DSA challenger enter the race at the behest of Mamdani.

Claire Valdez, a 36-year-old state assemblywoman, is running with Mamdani’s endorsement against Brooklyn Borough President Antonio Reynoso.

Both primary candidates, however, are seen as progressive, and they boast overlapping platforms ahead of Tuesday’s Democratic primary.

They share goals that include the abolishment of US Immigration and Customs Enforcement (ICE) and the end to US military aid to Israel, among other issues, but supporters say they offer different flavours of leftism.

The 43-year-old Reynoso has rallied the support of several labour unions and the progressive Working Families Party, while winning the endorsement of outgoing Congresswoman Nydia Velazquez, who currently represents the 7th District.

To illustrate his qualifications, Reynoso has pointed to his experience as a lifelong New Yorker who has helped build the city’s progressive movement.

Valdez, by contrast, is originally from Texas. She moved to New York in 2015 to pursue a career in the arts and says her experience with the city’s inequality inspired her to enter politics.

To many, she has become emblematic of the young, professional transplants who make up a large portion of the city’s inhabitants.

A Kennedy, a former Republican and an AI reformist

A more centrist Democratic primary is unfolding in New York’s 12th Congressional District, an affluent stretch of Manhattan spanning from the Upper West Side to the trendy Flatiron District.

Eight challengers are hoping to receive the Democratic nomination to replace outgoing Representative Jerrold Nadler, and outside groups are pouring millions into the race.

The candidates include Jack Schlossberg, the 33-year-old grandson of former US President John F Kennedy. Schlossberg has no experience in elected office, but has built a large online following with his unfiltered social media posts.

If elected, Schlossberg would be the seventh member of the Kennedy family to serve in Congress.

Other challengers include Alex Bores, a 35-year-old New York State assemblyman who has made AI regulation a top priority, and 44-year-old Micah Lasher, a fellow assemblyman whose career in politics stretches back to his teenage years.

Also in contention is George Conway, a 62-year-old erstwhile Republican who has been one of Trump’s most prominent critics.

During the president’s first term, Conway’s commentary stood out given that his wife, Kellyanne Conway, served as Trump’s senior counsel. The pair have since separated.

Early polls showed Schlossberg leading. But more recent surveys suggest Bores and Lasher have become the primary frontrunners.

Vulnerable Republican

The Democratic Party is seeking to pick up at least one Republican-held seat in the state of New York this November.

They have set their sights on incumbent Mike Lawler, a Republican who represents a Democratic-leaning district just north of New York City, in the Hudson Valley.

Despite the demographics in New York’s 17th District, the 39-year-old Lawler handily defeated Democratic incumbent Mondaire Jones in 2024. Five Democrats are now vying to win Tuesday’s Democratic primary in order to take him out.

Two of the challengers have taken the centrist route, including Cait Conley, a former US Army officer and White House national security adviser, and Beth Davidson, a county legislator.

Then there’s John Cappello, a retired member of the US Air Force, running on affordability concerns.

Racing on the progressive side are activist Effie Phillips-Staley, who has been endorsed by the Working Families Party, and Mike Sacks, a lawyer and journalist.

Conley has so far come out on top in a slate of recent polls.