With less than a month until Election Day, both parties are spending heavily across a wide House battlefield that could determine control of Congress in 2027. Republicans currently hold a narrow 218-214 majority. Campaign targets, planned advertising and outside spending point to more than 90 districts receiving attention in the final weeks. About 60 are priorities for both parties’ congressional campaign committees and Trump-aligned super PACs. Those shared battlegrounds favored Trump by an average of roughly eight percentage points in 2024, suggesting the contest has reached well beyond the closest districts on the map. The Cook Political Report lists 43 districts as competitive, including 22 toss-ups. That is up from 39 competitive races, 18 of them toss-ups, in its initial ratings in February 2025. But party spending extends well beyond those ratings: nearly half a billion dollars in advertising reservations have been placed for the period through Election Day. Some contests are competitive because voters recently split their tickets or because the previous result was exceptionally close. New York Republican Mike Lawler, Pennsylvania Republican Brian Fitzpatrick and Washington Democrat Marie Gluesenkamp Perez represent districts that backed one party’s presidential candidate but elected a House member from the other. Democrat Adam Gray won California’s 13th District by fewer than 200 votes in 2024, while Republican Mariannette Miller-Meeks prevailed in Iowa’s 1st by 799. The political climate has also shifted since the last presidential election. The report points to record-high disapproval of President Trump, voter concerns about the war in Iran, fuel costs, tariffs and immigration enforcement, as well as an unusually high number of congressional retirements and primary defeats. Those factors may test assumptions made by candidates and strategists using 2024 results to forecast this year’s races. Redistricting has added another layer of uncertainty. New maps in several states affect an estimated one in 10 registered voters. Republican-led legislatures pursued changes in states including Texas and Florida, while Democrats responded in California. Some new boundaries were drawn on the assumption that Trump voters would remain aligned as they were in 2024. Polling data from Strength in Numbers and Verasight indicate Trump’s approval is below average in communities within newly drawn districts in South Florida and along the Texas-Mexico border, including Texas’ 28th and Florida’s 25th districts. In North Carolina’s 1st District, Democrat Don Davis faces a more conservative electorate after redistricting, but a competitive Senate race and the broader political climate have helped keep the House contest in play. More than $20 million in advertising is scheduled there before Election Day. The Democratic Congressional Campaign Committee’s battlefield includes more than 90 districts: 46 in its Red to Blue effort, 26 held by vulnerable Democratic incumbents and 19 additional districts it considers in play. The National Republican Congressional Committee lists 17 vulnerable incumbents for support and 27 candidates running in open races or against Democratic incumbents. A place on a target list does not guarantee a close race. Many districts Democrats identify as in play gave Trump close to 60% of the vote in 2024 and have drawn little advertising from either side. Still, millions are flowing into some districts Trump carried by 15 points, including Kentucky’s 6th. In Arkansas’ 2nd, outside spending against Democratic nominee Chris Jones and in support of Republican incumbent French Hill helped prompt Democrats to add the race to their target program. Target lists have historically produced mixed results. From 2012 through 2024, Democrats won 34% of the districts they targeted, while Republicans won 29% of theirs, according to Ballotpedia tracking. Some ad reservations have also been canceled or redirected, including in Nebraska’s 2nd District, which both parties had targeted. Even with those changes, the scale of the remaining commitments shows that neither party is treating the House outcome as settled.