Republicans hold the House and Senate, but will that end the Washington gridlock even with President Trump?

Buoyed by the victory of Donald Trump, Republicans kept control of the House on Tuesday and hung on to their majority in the U.S. Senate, enshrining at least two years of single-party rule in Washington.

Democrats lost the chamber in 2014 and would have needed a net gain of five seats to retake the Senate with Trump in the White House.

They fell well short.

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Many experts and political analysts had predicted a Democratic takeover, given the daunting math facing Republicans — who had to defend far more seats — and Trump’s erratic campaign.

But just as they underestimated the Republican nominee, they failed to account for the resiliency of some of the GOP’s most endangered incumbents.

Republicans staked victories in every one of the hardest-fought contests, with one exception. In Illinois, Democratic Rep. Tammy Duckworth knocked off Mark Kirk, long seen as the most vulnerable GOP member of the Senate.

In Wisconsin, Ron Johnson had been all but written off by strategists in both parties. Instead, he handily fended off a comeback attempt by former Democratic Sen. Russell D. Feingold. In North Carolina, Richard M. Burr won a second term despite waging a lackluster campaign.

In Arizona, Sen. John McCain easily won a sixth term after the toughest challenge of his lengthy career and Sen. Roy Blunt of Missouri also withstood a more-difficult-than-expected fight. In Pennsylvania, Patrick J. Toomey won after casting himself in a bipartisan light and touting his work with Democrats on gun control.

Republicans, who currently hold 54 of 100 seats, also posted victories in two states once eyed by Democrats as promising takeover opportunities.

In Florida, Marco Rubio — a once and likely future presidential candidate — coasted to a second term after he reversed himself under pressure from GOP leaders and decided to seek another term. In Ohio, Rob Portman also won easy reelection after running one of the strongest campaigns in the country in a perennial battleground state.

In Indiana, former Sen. Evan Bayh disappointed Democrats by failing in his comeback attempt, losing the state’s open-seat contest after Republicans and their allies poured in resources for Rep. Todd Young.

In a bright spot for Democrats, Nevada’s attorney general, Catherine Cortez Masto, rallied to hang on to the U.S. Senate seat being vacated by the retiring Democratic leader, Harry Reid — becoming the first Latina in the Senate.

One contest remained too close to call: the New Hampshire race between incumbent Republican Kelly Ayotte and Democratic Gov. Maggie Hassan. Even if Hassan wins, Democrats would only net two seats.

The final makeup of the Senate will not be determined until the race in Louisiana is settled. Since no candidate won more than 50%, Republican state Treasurer John Kennedy will face Democrat Foster Campbell in a December runoff.

Apart from the presidential contest, nothing on Tuesday will do as much to shape the political outlook for the next two years as the fight for control of the Senate.

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Trump would have faced a much more difficult time if he won the presidency and faced a Senate in the hands of opposition Democrats.

Despite one-party rule, Tuesday’s results may not ease the partisan infighting or persistent gridlock that has defined Congress in recent years, to the great frustration of many voters.

Trump broke with Republican orthodoxy on several issues, including trade and foreign policy and that could set him against many congressional Republicans, including House Speaker Paul D. Ryan.

Ryan campaigned on the need for Republicans to have unified government, with control of Congress and the White House, but keeping lawmakers in line to actually pass legislation may prove difficult. Bringing Democrats on board for GOP priorities seems even more unlikely.

“I’m hard-pressed to think that Congress will be able to muster much more agreement with themselves or the incoming president,” said Sarah Binder, a political science professor at George Washington University and expert on Congress. “Most of the ingredients that have created this low-functioning Congress are still in place,” Binder said.

Part of the dysfunction in Congress could be eased if the new president played a more actively bipartisan role, reaching across the aisle much the way former President Bill Clinton did when he faced a Republican-held Congress, some analysts said.

Politically, however, there may be little incentive for the new president to court votes from the other side after such a deeply polarizing election.

Voters seemed equally skeptical of change.

“I thought Congress would get better when Jesse Helms retired,” said Mike Pedneau, an independent voter and retired mental health worker in Raleigh, N.C., referring to his state’s arch-conservative senator, who died in 2008.

“It’s gotten more brittle,” Pedneau said. “I’d almost rather have the other side win it if meant an end to gridlock.”

Republicans began the election cycle with a built-in disadvantage.

The GOP was forced to defend 24 seats versus 10 for the Democrats, and the party’s difficulties seemed to be compounded when voters picked Trump as their nominee.

His many controversial and insulting statements forced Republican candidates to either defend or condemn their presidential standard-bearer, antagonizing voters whichever they chose. Some repudiated Trump. Others contorted themselves by saying they would vote for the nominee but not endorse his candidacy.

More significant, Trump failed to invest in the kind of political infrastructure — such as voter identification and turnout operations — that are typically led by a party’s presidential candidate.

“Since Trump hasn’t been running a campaign as much as a concert tour complete with merchandise, many of [the] programs that usually help down-ballot candidates are bare bones or missing entirely,” Jennifer Duffy, a nonpartisan campaign analyst, wrote in the Cook Political Report.

That seemed not to matter, however, as Trump strongly outperformed past Republican presidential nominees in a number of states and especially among rural voters. They needed no prodding to turn out.

Polls waxed and waned through the fall, with Democrats gaining momentum in Senate and House contests as Clinton opened a substantial lead over Trump after his widely panned performance in three presidential debates.

But races tightened again after FBI Director James B. Comey sent a letter to Congress on Oct. 28 saying investigators would review a newly discovered trove of emails connected to Clinton’s private email server as secretary of State. By the time Comey released an all-clear letter Sunday, Democrats said several Senate seats had slipped beyond their grasp.

“He became the leading Republican political operative in the country, wittingly or unwittingly,” House Democratic Leader Nancy Pelosi (D-S.F.) told reporters during a brief stop Tuesday at Democratic National Committee headquarters in Washington.

In the House, Republicans held a 247-188 majority, the largest for either party since the 1930s.

Democrats lost control in 2010 and the 30-seat gain they needed to take back the House always appeared well beyond their reach, given district lines that favor sitting lawmakers and shelter most incumbents from serious challenge. They picked up four seats with several more contests still to be decided.

Twitter: @markzbarabak, @lisamascaro

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UPDATES:

12:10 a.m. Wednesday: This story was updated with Trump winning the White House.

9 p.m.: This article was updated with results from Wisconsin, North Carolina and Arizona.

This article was first published at 7:45 p.m. Tuesday.