When Republicans narrowly clinched control of the US House of Representatives, it was clear the “red wave” failed to materialize and Democrats avoided what many feared would be a hefty defeat.

Considering the midterm elections historically tend to favor the president’s opposing party, Democrats performed well. Despite Biden’s low approval rating, his administration had the best midterm performance of any president in decades.

That strong performance, especially in battleground seats, came about because the party was able to mobilize its base – greatly helped by the issue of abortion rights – while in many areas Republicans were hampered because extremist candidates, often espousing unpopular views around election denial, failed to deliver enthusiastic support.

Examining certain toss-up seats reveals the pattern that helped the Democrats over-perform expectations. A competitive House race is often defined by how close the results appear to be, as indicated by early polling and the district’s past performance in previous elections.

Ashley Koning, the director of Rutgers University’s Eagleton Center for Public Interest Polling, said: “If we’re talking about numbers, competitiveness would be something within the margin of error or a very small margin between two candidates in pre-election polling. Substantively, a competitive race would be where either candidate has a shot of winning and are both polling equal support throughout the election cycle.”

Koning added: “Democrats performed better in competitive races, and they certainly performed better where abortion was on the ballot either directly or indirectly.”

Exit polls showed issues like abortion rights were top of mind for voters, particularly women, as seen by the ballot measures passed to protect abortion access in all five states that held such votes.

In Virginia, often referred to as a bellwether state because its election results often match that of the nation, incumbent Democrats like Abigail Spanberger and Jennifer Wexton fended off their Republican challengers.

“That was a key indicator that the House would be in better shape for Democrats,” Koning said.

In Michigan, a swing state, not only did incumbent governor Gretchen Whitmer hold on to her seat, reproductive rights won big, too. Michigan voters opted to establish abortion protections in the state’s constitution. Before the election, Democratic House candidate Elissa Slotkin predicted that if the abortion ballot measure passed, she’d win her election. Slotkin ultimately won in the highly competitive seventh district.

“We’re seeing success for Democrats in such a swing state and such a competitive state time and time again in election cycles,” Koning said.

Another factor is the dismal performance by Republican candidates with extreme far-right views who aligned themselves with Donald Trump – a trend also seen in the losses of election deniers in nearly every statewide race.

“We saw that Republican candidates actually took quite a hit if they were extreme and/or backed by Trump,” Koning said.

In south Texas, Democrats re-flipped a seat in the 34th district when Vicente Gonzalez defeated far-right incumbent Mayra Flores, who won a special election earlier this year. Another Democrat, Henry Cuellar, held on to his seat in the state’s 28th district.

In Washington’s third congressional district, progressive Marie Gluesenkamp Perez didn’t just win her race against Trump ally Joe Kent, she also flipped the red seat blue.

Redistricting also played a crucial role in the nail-biting race for House control and could be responsible for some of the few Democrat reversals during the midterms.

In states like Michigan, California, Pennsylvania, North Carolina and New York, independent commissions and courts drew competitive maps that gave both parties a chance to compete for seats. In other states, like Texas, Florida and Illinois, lawmakers drew maps that were heavily distorted to favor one party over the other.

“On the whole, maps looked slightly better for Democrats than they did previously. Of course, it still did favor Republicans across the country, but really that’s state-by-state dependent. There were a number of gerrymandering court cases that came in the final weeks and months before the election,” Koning said.

One such court case was in New York, often thought of as a predictably blue state.

New York Democrats tried to gerrymander the state map in 2022 in favor of their party, but the map was thrown out by a state judge. The state then saw a wave of Republican House wins, like in district 17, where the incumbent representative and chair of the House Democrats’ campaign arm, Sean Maloney, lost to Republican Mike Lawler.

New York’s fourth district, which was expected to lean Democrat, was won by Republican Anthony D’Esposito.

In a press conference before the House was officially called for Republicans, Biden said: “Democrats had a strong night. And we lost fewer seats in the House of Representatives than any Democratic president’s first midterm election in the last 40 years.”