Kshama Sawant's lead continued to grow on Friday, prompting 16-year incumbent Richard Conlin to concede.
Even in this liberal city, Sawant's win has surprised many here. Conlin was backed by the city's political establishment. On election night, she trailed by four percentage points. She wasn't a veteran politician, having only run in one previous campaign.
But in the days following election night, Sawant's share of the votes outgrew Conlin's.
"I don't think socialism makes most people in Seattle afraid," Conlin said Friday.
While city council races are technically non-partisan, Sawant made sure people knew she was running as a socialist - a label that would be political poisonous in many parts of the country.
Sawant, a 41-year-old college economics professor, first drew attention as part of local Occupy Wall Street protests that included taking over a downtown park and a junior college campus in late 2011. She then ran for legislative office in 2012, challenging the powerful speaker of the state House, a Democrat. She was easily defeated.
This year, though, she pushed a platform that resonated with the city. She backed efforts to raise the minimum wage to $15; called for rent control in the city where rental prices keep climbing; and supports a tax on millionaires to help fund a public transit system and other services.
"I will reach out to the people who supported Richard Conlin, working with everyone in Seattle to fight for a minimum wage of $15 (an) hour, affordable housing, and the needs of ordinary people," Sawant said in a statement.
During her campaign, she condemned economic inequality, contending that some people aren't benefiting from the city's declining jobless rate, ongoing recovery from the recession, and downtown building boom.
"She's passionate about her values," Conlin said.
Research showed no socialist candidate had won a citywide office in the past 100 years. The last socialist candidate to make it into the general election was in 1991 and was defeated, said Scott Cline, the city's archivist.