This article has been updated with election results.
House Republicans expanded their majority on Tuesday night, joining their colleagues in the Senate and in statehouses in outperforming expectations. By defeating at least nine Democratic incumbents and losing just one of their own, Republicans put themselves in position to have the largest number of seats since 1949.
When Tuesday began, the most likely outcome in the House appeared to be a Republican gain of six to nine seats. But if the remaining races wind up as expected, a gain of between 10 and 15 seats now seems the most likely outcome.
While dozens of races remain to be called, and the likely range could change, Republican House candidates are having a strong night. They have defeated Democratic incumbents in Illinois, Iowa, New Hampshire, New York, West Virginia and Georgia while losing just one incumbent of their own, in Florida.
And as attention moves toward races in the West, there are close contests remaining in Maine, Maryland and Texas that could provide additional numbers for the G.O.P.
Expanded Republican Majority in the House Is Likely
Simulations of House elections conducted by YouGov, a polling and research firm, show the likeliest outcome for the G.O.P. is between 236 and 241 seats.
In most cases, including districts previously held by the G.O.P., the newly elected Republicans are more conservative than the lawmakers they are replacing, according to ideological scores calculated by Crowdpac.
Florida provided a small respite for Democrats, with Gwen Graham defeating Steve Southerland, the Republican incumbent, in the Second District.
But Democrats struggled in other races. In Florida’s 26th District, west of Miami, Carlos Curbelo, a Republican, beat Joe Garcia, the Democratic incumbent. John Barrow, a Georgia Democrat who has repeatedly fended off Republican challengers, fell to Rick Allen, a Republican, by 16 points. In West Virginia, Nick Rahall, a longtime Democratic congressman, lost to Evan Jenkins by double digits. Mike Bost, an Illinois Republican, soundly defeated Bill Enyart, a freshman Democrat, in the 12th District. In New York, Republicans beat two Democratic incumbents, Timothy Bishop on Long Island and Dan Maffei from the Syracuse area, and Michael Grimm easily won re-election to his Staten Island district despite facing a 20-count federal indictment.
The Republicans began the night with a likely three-seat advantage, thanks to retiring Democrats who hold districts that probably will elect a Republican. The G.O.P. has already won North Carolina’s Seventh and New York’s 21st, where Elise Stefanik, 30, a former White House aide, became the youngest woman elected to Congress, and is expected to win in Utah’s Fourth.
Democrats have few remaining shots at flipping a seat currently held by a Republican, with perhaps the best chance in California’s 31st District, where Gary Miller is retiring in a district that leans Democratic.
Earlier, Republicans held open seats in Virginia’s 10th District, where Barbara Comstock defeated John Foust, and Pennsylvania’s Sixth District.
The Republicans started with 233 of the 435 seats (with three vacancies). If things go as expected for Democrats, they could wind up with their lowest total since 1949, when they had 188 seats. (They had 193 after the 2010 elections.)
But lodged within the 435 House races is a question that becomes even more important when the next Congress convenes on Jan. 3: What kind of Republicans are the new members? In some cases, retiring or defeated House Republicans will be replaced by more conservative lawmakers. For the Republican leadership, more Republicans is a good thing, but some of the newcomers — unencumbered by the likelihood of a general election challenge or the memory of being in the minority — may be harder to manage than their predecessors.
There were 22 tossup House races on Tuesday morning, and an additional 18 that leaned slightly toward one party or the other, according to the Cook Political Report. The relatively small number of seats in play was reflected in the outside spending on House races in October, which was down 31 percent compared with 2010. But those seats that are contested have gotten a lot of attention from contributors.
In Arizona’s Second Congressional District, for example, the first independent expenditure came on March 21, 2013, nearly 20 months before the election. That race, between Ron Barber, the incumbent Democrat, and Martha McSally, a Republican and retired Air Force colonel, was very close early Wednesday morning.
In Utah, Mia Love is poised to become the first black Republican woman elected to the House, replacing a retiring Democrat. And California offers no less than six competitive races, with Republicans having a chance of unseating four freshman Democrats. Republican wins here would be a final blow to Democrats.
Finally, an open seat in Hawaii offers Charles Djou, a Republican, the chance to win back his old job, with a three-way governor’s race as the backdrop.
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