GEOFF BENNETT: Progressive Democrats dominated last night's midterm primary elections in New York in a resounding show of strength for the Democratic socialist mayor of New York City.

All three candidates endorsed by Mayor Zohran Mamdani won their races, two of them ousting sitting congressmen.

Darializa Avila Chevalier, a Democratic socialist, beat five-term incumbent Adriano Espaillat in New York's 13th congressional district.

Claire Valdez, another Democratic socialist, won the open seat primary in New York's Seventh Congressional District.

And Brad Lander bested incumbent Congressman Dan Goldman in New York's 10th Congressional District.

Lander won by some 30 points in a race that heavily focused on the candidates' differences over Israel policy.

BRAD LANDER (D), New York Congressional Candidate: Democrats are painfully divided by our differences over the U.S.

relationship to Israel and Palestine, and we have to face up to it squarely.

Our party needs to admit that Joe Biden's hug Bibi strategy was a catastrophic failure.

(CHEERING) REP.

DAN GOLDMAN (D-NY): The enemy to all that we want and all that we hope for is in the White House, not in our own party.

(CHEERING) GEOFF BENNETT: President Trump, for his part, responded to the results in several social media posts, one saying -- quote -- "America the beautiful will never be a communist country."

To break it all down, we're joined by Brigid Bergin, senior politics reporter for New York Public Radio.

Brigid, thanks for being with us.

BRIGID BERGIN, WNYC: Great to join you.

GEOFF BENNETT: So, the mayor of New York City, Mayor Mamdani, he spoke at one of the victory parties last night.

Here's a bit of what he had to say.

ZOHRAN MAMDANI (D), Mayor of New York City: We are showing that last June a year ago tomorrow was not an anomaly.

(CHEERING) ZOHRAN MAMDANI: It was not the end.

It was the beginning.

(CHEERING) GEOFF BENNETT: So, how much of what we saw last night is unique to New York City politics, its demographics, its activist networks, its political culture, and how much should Democrats elsewhere view as a signal of what might come in the November midterms?

BRIGID BERGIN: Yes, I mean, I think it's fair to say that Democratic politics in the country have their roots right here in New York City.

It's where Democratic House Leader Hakeem Jeffries represents a district in Brooklyn, and it's also where Senate Minority Leader Chuck Schumer is from, also in Brooklyn.

And so I think part of what we're seeing here is, when we talk about a challenge to the establishment, that challenge lands right at the footsteps of the leaders of the Democratic Party.

I think it is likely, as we are seeing in elections in other parts of the country -- I think of the mayor of Washington, D.C., as a recent example -- an increased number of Democratic socialist candidates running for office and potentially challenging incumbents.

And, as in the case of New York City, they may be successful.

GEOFF BENNETT: These Democratic socialists, how do they define themselves?

What are their policy goals?

What distinguishes them from mainstream Democrats?

BRIGID BERGIN: So, they center working-class New Yorkers, in this case, and they censor the needs of those individuals.

They are definitely more pro-Palestinian and take a lot of objection to the current position of the Democratic Party or its traditional position when it comes to Israel and being an ally of Israel without question.

They also take a strong stand on things like Medicare for all, making sure there's universal childcare, essentially talking about making more accessible benefits that would make the lives of working people easier.

GEOFF BENNETT: And how significant was the Gaza issue in the outcomes last night?

BRIGID BERGIN: I mean, that was a big issue in multiple races.

It certainly was at play in the Seventh Congressional District, where we saw assembly member Claire Valdez defeat Brooklyn Borough President Antonio Reynoso.

Both of them have called what has happened in Gaza a genocide.

But the issue there was that Valdez has been someone who has been outspoken on this that issue sooner.

Similarly, we saw in the 13th Congressional District, where Darializa Avila Chevalier defeated incumbent Representative Adriano Espaillat.

One of her main lines of attack was that they needed to support more in the district to pay for babies, not bombs, was her line.

And, in particular, she went after Espaillat for not doing more to help Mahmoud Khalil.

He is a Palestinian activist who she worked with as part of their pro-Palestinian anti-Israel encampments at Columbia University.

Mahmoud Khalil was arrested by ICE in the district.

And when they reached out to Espaillat's office for help, they say they did not get the help that they needed from their representative.

Khalil and his wife went on to make an ad that was paid for by a super PAC that supported Avila Chevalier.

So I think you see that was an issue that was certainly animating voters in that district as well.

GEOFF BENNETT: In the 30 seconds we have left, what did these results say about Mamdani's influence right now in New York City politics?

BRIGID BERGIN: There was a get-out-the-vote rally in Brooklyn just before primary day with Vermont Senator Bernie Sanders.

And at that rally, Mamdani said he's often asked about the state of the Democratic Party.

He said it needs to change.

And he's also asked, when does 2028 begin?

And he said it begins now.

It begins on primary day.

And I think he and the Democratic Socialists of America are looking to have a big influence going forward, specifically in 2028.

GEOFF BENNETT: New York Public Radio senior politics reporter Brigid Bergin.

Brigid, thanks, as always.

BRIGID BERGIN: Thanks, Geoff.