The outcome will determine whether the next president has a legislative-branch ally or antagonist in the fight ahead over Donald Trump's expiring tax cuts as well as clashes over immigration and Wall Street regulation. An opposition-controlled House could also block presidential spending initiatives and hinder the administration with partisan investigations.

Democrats need a net gain of just four seats to take the House majority from Republicans. And GOP incumbents are playing defense in 10 competitive races in the two reliably Democratic states.

Control of the House ultimately hinges on a complex map of about 40 competitive local campaigns. Most of those are along the coasts or the U.S. border with Mexico. 

In an era of regional political polarization and ruthless gerrymandering of district boundaries, more than 90% of 435 House races are not particularly competitive. 

"It's absolutely a fact that control of the House could go either way," Jacob Rubashkin, deputy editor of Inside Elections, which provides nonpartisan political analysis of congressional campaigns, said. 

A strong election performance by either Vice President Kamala Harris or Trump could tip the balance. But Joshua Huder, a senior fellow at Georgetown University's Government Affairs Institute, said idiosyncratic results in just a couple of states could also break the current "dead heat," regardless of the presidential winner.

Here is a survey of the contest:

New York-Northeast

Democrats are targeting five GOP-held seats in New York state, seeking to oust first-term Republican incumbents from the New York City suburbs on Long Island and the Hudson Valley, as well as one in the Syracuse area. 

These contests  — including a marquee showdown just north of New York City between freshman Republican Representative Mike Lawler and former Democratic congressman Mondaire Jones — are a major focus of House Democratic leader Hakeem Jeffries, who is from New York. 

First-term Representative Anthony D'Esposito, who represents much of Long Island's Nassau County, was already in a fiercely competitive race when he became enmeshed in scandal. The New York Times reported in September that he gave taxpayer-funded jobs to both his fiancee's daughter and another woman described as his lover.

National issues such as the economy and cost of living, abortion rights and immigration are prominent in these races. But so are local concerns, including an influx of migrants into New York City and the Hudson Vally, the financial burden of a $10,000 limit imposed on deductions for state and local taxes as part of Trump's federal tax overhaul, and high housing costs.

There are also high-profile House races in New Jersey, Eastern Pennsylvania and Maine. First-term New Jersey Republican Tom Kean Jr., the son of a former New Jersey governor with the same name, faces a strong challenge in an affluent suburban district that Joe Biden won in 2020.  

In Eastern Pennsylvania, three-term Democrat Susan Wild won her last election by fewer than 6,000 votes and again faces a struggle in a district that includes Allentown and the Lehigh Valley. Six-term Democrat Matt Cartwright is struggling to hold onto a perpetually competitive northeast Pennsylvania district that includes Biden's hometown Scranton but Trump carried in 2020.

Three-term Democratic incumbent Jared Golden is defending his seat in Maine's heavily rural 2nd Congressional District, the largest US House district by land area east of the Mississippi River. Trump won the district in the last presidential election.

West Coast

Southern California and that state's Central Valley hold another pocket of Republican-held seats that are among the most competitive nationally — and crucial to Democrats' hopes of taking the majority. 

Among them is a rematch to represent a heavily agricultural stretch of the San Joaquin Valley between first-term Republican John Duarte and Democrat Adam Gray, a former state representative. Duarte eked out his victory last time by just over 500 votes in a district Biden carried in 2020. 

Another hotly contested race in an area north of Los Angeles pits GOP Representative Mike Garcia against Democrat challenger George Whitesides, a former NASA chief of staff and chief executive of Virgin Galactic for a decade.

Many of the competitive California contests are in the Los Angeles media market, making them among the most costly in the US. Concerns over housing and gasoline costs, as well as water issues, figure in the races along with dominant national issues.

Seats held by Democrats in Washington and Alaska face fierce challenges, as does a seat held by a Republican in Oregon.

Heartland

A handful of seats in the Midwest and Great Plains held by Republicans are either competitive or edging in that direction, including two in Iowa. 

Nebraska's unusual method of apportioning its presidential Electoral College votes is adding to the pressure on Republican incumbent Don Bacon, who represents an Omaha-area swing district Biden carried in 2020. Nebraska is one of only two states that divides its electoral votes rather than awarding them as one bloc, allocating three of its five to the presidential candidate winning each of its three congressional districts.

That has stoked Democratic enthusiasm and Bacon is trailing in some polls.

In Iowa, GOP representatives Mariannette Miller-Meeks and Zach Nunn are in competitive contests, as Harris boosts Democratic enthusiasm and the state's strict abortion ban is triggering a backlash.

Republicans are targeting two seats in Michigan being vacated by Democrats. GOP challengers are focusing on inflation and fears the shift to electric vehicles will hurt the region.

Southwest

Republicans, who have made a tough stance on immigration a pillar of their campaign, see a pick-up opportunity in a New Mexico district that runs along the southern border. The seat, now held by first-term Democrat Gabe Vasquez, has switched back and forth between parties in each of the past three elections.

In Arizona, a ballot initiative to restore abortion rights in the state is feeding Democratic hopes of turning out enough voters to take a district held by a first-term Republican Juan Ciscomani, and a Phoenix-area seat held by a more-senior Republican, Dave Schweikert. Republicans hope concerns over immigration will save the incumbents.

Southeast

Election night viewers can look to two seats in Virginia, and another in North Carolina, as potential early bellwethers. Polls close at 7 p.m. New York time in Virginia, where economic issues mark competitive races for a central Virginia seat being vacated by a Democratic gubernatorial candidate Abigail Spanberger, and another on the state's Atlantic coastline defended by GOP Representative Jen Kiggans.

In eastern North Carolina, where polls will close at 7:30 p.m. New York time, a changing population and redistricting is giving the GOP a shot at unseating first-term Democratic Representative Don Davis.