The math behind a Democratic wave — or a GOP upset

Data: The Downballot and Sabato's Crystal Ball at the University of Virginia Center for Politics. (Balance of power accounts for opposing party gains due to redistricting.) Map: Kavya Beheraj/Axios Redistricting has helped House Republicans build a seawall that can withstand a roughly 5-point Democratic wave.

Why it matters: Early readings are pointing to something twice that size — enough to wash away the GOP House majority.

Democrats have been running roughly 10 points ahead of their 2024 presidential performance in special elections this year.

A swing of that magnitude would produce a comfortable 230-205 Democratic majority, according to an Axios analysis of how the battle for the House would play out under different electoral scenarios.

Between the lines: Gerrymandering since the presidential election has given Republicans more breathing room , with GOP-drawn maps creating a net advantage of roughly nine seats.

But some of those newly redrawn GOP seats rest on a potentially shaky assumption: that the 2026 electorate will look much like 2024's.

A national swing toward Democrats like the one in Trump's first midterm would overwhelm the GOP's redistricting defenses.

By the numbers: The current generic ballot has Democrats up roughly 6 points , which would produce a 221-214 Democratic majority in the Axios analysis.

That's a workable majority, but not an overwhelming one.

By comparison: In 2018, the national House vote swung 6½ points toward Democrats from the 2016 presidential baseline.

Democrats picked up 40 seats, producing a 235-199 majority (one seat was unresolved).

The other side: If Republicans outperform Trump's 2024 numbers by 5 points across congressional districts, the new maps would give them a massive 253-182 majority.

If 2026 simply looks like 2024 — with GOP candidates winning every district Trump would've carried under the new maps, including Trump districts where Democrats held on in 2024 — Republicans would net 16 seats, producing a 236-199 majority.

State of play: Two months before Election Day, Democrats can taste the House majority, provided two conditions hold: President Trump remains unpopular , and vulnerable Republicans stay close to him.