Persis Yu ousts Sen. Mike Rush

Persis Yu began her day voting at the Hyde Park Municipal Building, before heading on a tour of the suburban communities and Boston sections of the Norfolk Suffolk Senate District.

“We went to every town and every neighborhood,” she said Tuesday afternoon, standing in front of the Holy Name Parish in West Roxbury. “We made the rounds of the whole district, which is what we did in this campaign.”

Incumbent Norfolk Suffolk District Sen. Michael Rush kicked off his election day campaigning with Mayor Michelle Wu and District Attorney Kevin Hayden as the trio brought coffee and donuts to poll workers at the St. Nectarios Greek Orthodox Church in Roslindale.

By the end of the day, Yu’s investment in shoe leather and tire treads appeared to pay off. With some mail-in votes still yet to be counted, Yu’s numbers by 11 p.m. showed her with a 546-vote lead over Rush, who has not faced a challenger since 2010, when he was first elected to represent the district.

At 11:15 p.m., after her team crunched numbers in the basement of the Substation in Roslindale Square and were all but certain of their victory, Yu emerged to address supporters.

“What we did, many thought was impossible,” she said. “We took on an entrenched candidate with the full weight of the establishment and full money of the establishment behind him. We reached thousands of people. We built a movement, and we scared them.”

Yu’s victory comes amid somewhat of a reckoning for the Democratic Party, both in Massachusetts and nationally as voters are looking for solutions to pressing problems — high rents, unaffordable health care, a tax system that gives billionaires and corporations a pass.

At the top of the Democratic ballot in Massachusetts, U.S. Rep. Seth Moulton mounted a centrist, pro-corporate challenge to progressive U.S. Sen. Ed Markey and suffered a landslide loss, capturing just 35.2% of the vote to Markey’s 64.8%. In Boston, the margin was even higher, with Markey claiming 74.1% of the vote.

In the Second Middlesex District, soon to be vacated by Sen. Pat Jehlen, Democratic Socialists of America member Erika Uyterhoeven won the primary vote, finishing seven points ahead of progressive Democrat Christine Barber.

In the three contested Boston-based state Senate districts, results were more mixed. Progressive Democrat Latoya Gayle challenged 1st Suffolk Sen. Nick Collins, but despite backing from Mayor Michelle Wu, finished 10 points behind him. Former Wu staffer Daniel Lander is locked in a dead heat with incumbent Suffolk and Middlesex Sen. William Brownsberger with a narrow 20 vote lead as of Wednesday afternoon.

While Rush also had backing from Wu, Yu beat him handily in Boston with 67% of the vote to Rush’s 32%. That gave Yu a 2,389-vote lead over Rush. Rush won all four towns in the suburban portion of the district — Walpole, Norwood, Dedham and Westwood — but his gains were in the hundreds and were not enough to offset Yu’s wins in Jamaica Plain, Hyde Park, Roslindale and West Roxbury.

Outside the Phineas Bates School, where Wu voted Tuesday morning and posed for photos with Rush, Yu’s supporters outnumbered Rush’s five to one.

Speaking to The Flipside at the Substation, Yu attributed her victory to voters’ desire for change.

“People want a better economy to take care of their families and a legislature that is accountable to them, not to leadership in the State House,” she said. “People want bold ideas. They want a north star. To know there’s something we’re working towards. People want to hear what’s possible, not what the constraints are."

Yu’s party went on late. By 11:30, her campaign still hadn’t claimed an outright victory. But the mood in the Substation was jubilant.

“This has been a wild ride,” Yu told her supporters. “We have knocked on nearly 25,000 doors. We have made over 10,000 phone calls, done dozens of stand outs, attended countless neighborhood events and parades, and let’s be clear: Nobody has ever had more fun than we have.”