Democratic pollster Anna Greenberg on Thursday said Republican incumbents are experiencing never-before-seen signs of weakness.

"If you look at Washington, for example, they have a jungle primary there, so they've got Republicans and Democrats running in the same election, and you've got people like [Rep.] Cathy McMorris Rodgers Cathy McMorris RodgersHillicon Valley: Trump backs potential Microsoft, TikTok deal, sets September deadline | House Republicans request classified TikTok briefing | Facebook labels manipulated Pelosi video Top House Republicans request classified TikTok briefing More than 100 lawmakers urge IRS to resolve stimulus payment issues MORE [R-Wash.] getting 43 percent in the jungle primary," Greenberg told Hill.TV's Joe Concha on "What America's Thinking."

"You just see signs of weakness for Republican incumbents that I don't think anybody ever thought would be in trouble," she said.

Sabato's Crystal Ball moved Washington's 5th District, which McMorris Rodgers has held since 2005, from leaning Republican to a toss-up on Wednesday.

McMorris Rodgers is a member of GOP leadership as the House Republican Conference chair.

Republicans are also seeing worrying signs in other traditionally red districts. In Ohio's 12th Congressional District, the Republican candidate is holding on to a razor-thin lead after Tuesday's special election in a district that President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE won by 11 points in 2016.

The Cook Political Report said on Thursday that Democrats outperformed its projections in nine special House elections.

Democrats need 23 seats in the House and two in the Senate in order to take back both houses of Congress in November. Many GOP-held House seats, though, are already likely to fall into Democratic hands. That means Democrats may need to win as few as 15 competitive seats to retake the House.

— Julia Manchester