ANALYSIS — With a majority comes greater vulnerability. To retain control next year, more than a handful of House Republicans are going to have to win in potentially hostile partisan territory and get some voters to buck their partisan preference.

Republicans are defending eight of the dozen House races rated as a Toss-up by Inside Elections. And Democrats have a structural advantage in seven of the eight GOP-held seats, according to Inside Elections’ Baseline metric. 

Baseline captures a state or congressional district’s political performance by combining all federal and statewide election results over the past four election cycles into a single score. More specifically, it’s a trimmed mean of all of those results, throwing out the highest and lowest performances and averaging the rest. Baseline seeks to approximate what the “typical” Democrat or Republican might receive in any given district. With multiple races across multiple cycles, the metric should make it more difficult for an anomaly to skew the measurement.

New York Republicans Anthony D’Esposito and Mike Lawler are running for reelection in the most difficult districts. Democrats have an 11.7-point advantage (55.4 percent to 43.7 percent) in D’Esposito’s 4th District and a 10.3-point edge (54.3 percent to 44 percent) in Lawler’s 17th District, according to Baseline. Democrats also have more than a 5-point advantage in the 3rd and 22nd Districts, represented by GOP Reps. George Santos and Brandon Williams, respectively. 

Outside of the Empire State, Democrats have a Baseline advantage in three more Toss-up districts currently represented by a Republican. They’ve got a 3.7-point edge (51.6 percent to 48 percent) in California’s 27th District, represented by Mike Garcia, and a 1.2-point edge (50.4 percent to 49.2 percent) in California’s 13th District, represented by John Duarte. 

Farther north in Oregon’s 5th District, GOP Rep. Lori Chavez-DeRemer is running for reelection in a district where Democrats have a 2.3-point advantage (48.2 percent to 45.8 percent). She was first elected in 2022 by just more than a point. 

First-term Rep. Thomas H. Kean Jr. is the only Republican running for reelection in a Toss-up race where Republicans have a Baseline advantage. Republicans have a 4.3-point edge (51 percent to 46.7 percent) in New Jersey’s 7th District. 

Rep. Marie Gluesenkamp Pérez faces the most difficult terrain of the Democratic seats rated as Toss-ups. Republicans have an 8.1-point Baseline advantage (53.7 percent to 45.6 percent) in Washington’s 3rd District. Democratic incumbent Mary Peltola of Alaska also faces a challenging race in a state with a 13.2-point GOP edge, but Alaska’s top four, ranked-choice system should make it a little easier. 

First-term Democrats Yadira Caraveo of Colorado and Gabe Vasquez of New Mexico are also in Toss-up races, but their districts slightly favor Democrats, according to Baseline. Democrats have a 2.2-point edge (49.6 percent to 47.4 percent) in Colorado’s 8th District and a 5.9-point advantage (52.1 percent to 46.2 percent) in New Mexico’s 2nd. Democrats also have a 5-point edge in Michigan’s 7th District, which is open because Democratic Rep. Elissa Slotkin is running for the Senate.

According to Baseline, the most evenly divided district in the country is Arizona’s 6th District, represented by GOP Rep. Juan Ciscomani. The race is currently rated Tilt Republican by Inside Elections.

Overall, Inside Elections rates 66 races as competitive, including 25 seats that favor Republicans and 29 that favor Democrats in addition to the 12 Toss-ups. Races in Ohio and North Carolina haven’t been rated yet, pending new maps.

Democrats need a net gain of five seats for a majority in the House. Control is within reach, although uncertainty with the presidential race at the top of the ballot and potentially new congressional lines in Alabama, Louisiana, Georgia, New York, Wisconsin and elsewhere will have an effect on the fight for the majority.

Nathan L. Gonzales is an elections analyst with CQ Roll Call.