Historically few number of midterm seats will decide control of U.S. house

The U.S. Capitol building in Washington, D.C., US, on Wednesday, July 23, 2025. Photo by Graeme Sloan /Bloomberg

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A shrinking number of seats will determine control of the U.S. House after both Republicans and Democrats spent much of the past year redrawing congressional maps to erase swing districts.

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Even before Florida’s legislature approved a new Republican-leaning map last week, just 16 seats were listed as “tossups” by the Cook Political Report, the nonpartisan newsletter that serves as an unofficial electoral scorekeeper. Another 16 districts are listed as leaning toward Democrats or Republicans, with the outcome all but predetermined for more than 400 seats.

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This could make for the fewest competitive seats since political analyst Charlie Cook first published his race ratings in 1984. That means even if historical trends and current events favour Democrats heading into November, they’re likely to fall short of the 41 districts they picked up in the 2018 midterms during the first Trump administration.

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“There aren’t really 40 seats on the board potentially right now just because of redistricting and that polarization,” said Carrie Dann, managing editor of the Cook Political Report.

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That reality allows the two political parties to concentrate their resources. The Democratic House campaign operation lists 44 Republican districts in play, and the GOP equivalent is aiding 17 challengers hoping to unseat Democratic incumbents.

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Those numbers can change after primary elections, but one Republican operative familiar with the party’s plans said the total number of contested seats is about half those the parties fought over in the last midterm election in 2022.

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Republicans say the smaller map favours them. Before the most recent spate of map changes, only three Republican House members were elected in districts that Democrat Kamala Harris won in 2024 — compared to 13 Democrats defending seats that President Donald Trump won.

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Zach Parkinson, a spokesman for the Republican National Committee, said his party has better campaign infrastructure in place.

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“Part of that right now is financial, but part of it is also we’re all very synced up with the president, the White House,” Parkinson said. “Everyone on our side institutionally is rowing in the same direction.”

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But Democrats note that Republican efforts to aggressively gerrymander districts in Texas and Florida could leave them even more vulnerable if Democrats leverage the same kind of voter enthusiasm they did in 2018, when they won enough seats to take back the House majority.

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John Bisognano, president of the National Democratic Redistricting Committee, said congressional districts in Texas and Florida were already designed to favour Republicans.

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“So what you need to do in order to create a deeper gerrymander is make more Republican seats competitive,” he said. “As the Democratic advantage grows, the likelihood and opportunity for dummymanders increases.”

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A dummymander happens when one party gerrymanders so aggressively that it spreads its majority too thin — making its seats more vulnerable if the other party performs better than expected.