WASHINGTON — Representative Dan Lipinski, a conservative Democrat from Illinois whose opposition to abortion rights and the Affordable Care Act made him a pariah in his party, lost a hard-fought primary race on Tuesday night to his progressive challenger, Marie Newman.
Ms. Newman, a business consultant and founder of an anti-bullying program, edged out Mr. Lipinski by two percentage points, with 493 of 500 precincts reporting early Wednesday. She had the backing of the progressive group Justice Democrats and its standard-bearer, Representative Alexandria Ocasio-Cortez of New York, as well as Emily’s List, the powerful group that backs Democrats who support abortion rights.
Mr. Lipinski narrowly beat Ms. Newman in 2018. Tuesday’s results were a major upset for the congressman, whose family has represented Illinois’ third district, in the Chicago suburbs, for nearly four decades. Mr. Lipinski’s father, Bill Lipinski, first won the seat in 1982 and held it until 2005, when Mr. Lipinski succeeded him.
“This is a critical victory for the progressive movement in showing that voters are ready for a new generation of progressive leadership in the Democratic Party,” said Alexandra Rojas, executive director of Justice Democrats. “This isn’t just a loss for one incumbent. It’s a defeat for machine politics and big corporate donors who want to stop our movement for ‘Medicare for all,’ a Green New Deal and reproductive rights.”
Ms. Newman’s victory was a rare bright spot for the progressive movement in Tuesday’s contests, in which Senator Bernie Sanders of Vermont suffered major defeats in three crucial states, including Illinois. The results all but extinguished his hopes of a comeback against former Vice President Joseph R. Biden Jr., who appeared to be headed toward becoming the Democrats’ presumptive nominee.
The race put a fine point on the tensions within the Democratic Party in the era of President Trump. Mr. Lipinski’s views are far more conservative than those of Mr. Biden, and in many ways he was an outlier among Democrats. In addition to voting against the 2010 health care law and opposing abortion rights, he declined to endorse former President Barack Obama in 2012 and opposed same-sex marriage until the Supreme Court made it legal across the nation in 2015.
Despite their official stance that the party backs incumbents, top Democrats did not go out of their way to advance Mr. Lipinski’s cause. During a trip to Texas last month, with 10 days to go until the state’s primary, Speaker Nancy Pelosi dropped in on the campaign offices of another conservative Democrat, Representative Henry Cuellar, boosting his successful battle to defeat a Justice Democrats-backed challenger, Jessica Cisneros. Ms. Pelosi did not do the same for Mr. Lipinksi.
And Mr. Lipinski’s fellow Illinoisan, Representative Cheri Bustos, who leads the party’s campaign arm, canceled a planned fund-raiser for Mr. Lipinski last year, bowing to progressives who were outraged by the congressman’s anti-abortion rights stance. Her decision raised questions about whether there was room left in the party for lawmakers who oppose abortion.
The day after Ms. Ocasio-Cortez endorsed Ms. Newman, Representative Steny H. Hoyer of Maryland, a centrist Democrat and the majority leader, told reporters that there was “absolutely” room in the party for candidates who oppose abortion rights. But some veteran rank-and-file Democrats, including two others from Illinois, Representatives Jan Schakowsky and Luis Gutiérrez, openly backed Ms. Newman.
Ms. Newman, who worked in advertising before starting her own consulting business, founded a nonprofit organization, “Team Up to Stop Bullying,” after one of her children was subjected to severe bullying in school. Her campaign website bills her as “a state and national advocate for health care rights, income equality, LGBTQ+ rights, and common-sense gun safety.”
Ms. Newman had the backing of groups that support abortion rights, including Planned Parenthood and Naral, as well as several unions and Indivisible, the grass-roots advocacy group. Even before all the votes were counted on Tuesday night, Emily’s List issued a statement congratulating her on the victory, calling her “a proven fighter for working families.”