Preliminary election results show Wiener with 41% of the vote and Chan with about 29%. Saikat Chakrabarti placed third with nearly 15% of the vote and has dropped out of the race.
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Wiener and Chan are now set to compete for California's 11th Congressional District seat, which represents San Francisco.
At his campaign office in San Francisco, Wiener pointed to his record in challenging federal policies under former President Donald Trump.
"San Franciscans have seen that I have gone to the mat for this community against Donald Trump, whether banning ICE from wearing ski masks or the bill that I have moving through the legislature now to allow people to sue ICE and Border Patrol and other federal agents who violate people's rights, or the work I'm doing right now to expand science research funding in California as Trump tries to destroy scientific research," Wiener said.
Chan spoke at an event in Chinatown. She has framed her campaign as representing working people. The progressive Democrat expressed gratitude for her advancement as she prayed and lit incense and looked ahead to November.
"Seeing the Trump administration is cutting our health care, cutting our education, cutting our social security, this is a moment that working people must have a voice. And I think that our campaign embodies that. This is the reason why we're the only campaign that's endorsed by teachers, nurses and firefighters and so many working people, like hotel workers and trade workers, because we know and they know that this is part of their campaign. And when we're in Washington, D.C., they know that they will have not only a voice, but actually a seat at the table," Chan said.
Pelosi endorsed Chan on May 18, a move that political analysts say boosted her campaign.
"I think Nancy Pelosi's endorsement was a big deal for her. I think it really caused a lot of movement towards her. And, I think, Chakrabarti's campaign at the end of the day didn't close the deal with a lot of left progressive voters," said Jason McDaniel, an associate professor in the Department of Political Science at San Francisco State University.
McDaniel said the district carries significance beyond the city, given its unique boundaries and political influence.
"It's one of the few congressional districts that is a city, an entire city. It's interesting to think about that this really represents kind of where the city is. And of course our city resonates around the country and around the world with what it stands for sort of liberal and left progressive politics. It's been where the Democratic Party has moved to over the decades," McDaniel said.
The November election will determine who represents San Francisco in Congress as Pelosi steps away from the seat she has held for decades.