It's not official yet, but it looks like a primary challenger, endorsed by the Working Families Party and Democratic Socialists of America, beat a four-term Democratic incumbent to become the Democratic nominee and likely next mayor of New York's second-largest city. Via the New York Times:

A progressive challenger running her first campaign was poised on Tuesday to beat Buffalo’s four-term Democratic mayor in a primary upset that would upend the political landscape in New York’s second-biggest city and signal the strength of the party’s left wing.

The challenger, India B. Walton, is a former nurse and community activist who ran with the support of the Democratic Socialists of America and the Working Families Party. She was leading Byron Brown, a longtime member of the Democratic establishment, by 7 percentage points, or about 1,500 votes, as of midnight with all of the in-person ballots counted, according to unofficial results.

Should Ms. Walton, 38, win the primary and then triumph in the general election November — a likely result in heavily Democratic Buffalo — she would be the first socialist mayor of a major American city since 1960, when Frank P. Zeidler stepped down as Milwaukee’s mayor. She would also be the first female mayor in Buffalo’s history.