Bush is the fifth left-wing Democrat to oust an incumbent member of Congress from her party since the start of Trump’s presidency — including three this year — and her victory came as a welcome jolt for liberal activists working to challenge entrenched Democrats. A constellation of liberal organizations that helped push Bush to victory are now turning their focus on defeating other establishment figures, such as Rep. Richard E. Neal (D-Mass.), the powerful chair of the House Ways and Means Committee…

Along with victories in other open-seat primaries earlier this year, liberals will have a larger presence inside the House Democratic Caucus next year. This could give them a broader platform to push the potential Biden administration and House Speaker Nancy Pelosi (D-Calif.) to embrace their more aggressive agenda on health care and climate issues.

But Pelosi’s allies noted that she has had a stronger grip on her caucus in her second stint as speaker than she did a decade ago, and she has so far not faced the problems that drove John A. Boehner (R-Ohio) out as speaker in 2015 when conservative firebrands demanded his ouster.