WASHINGTON — Republicans held onto their slim Senate majority, a stinging blow to Democrats in a night full of them. Democrats had been nearly certain of retaking control but saw their hopes fizzle as endangered GOP incumbents won in Missouri, Pennsylvania, North Carolina and even Democrat-friendly Wisconsin.

GOP-held New Hampshire remained too close to call on Wednesday morning, but even if Democrats eked out a win there it would not make a difference.

Republicans started the night with a 54-46 majority in the Senate and were on track to end up with at least 52 seats, presuming they win a December runoff in Louisiana, as expected.

The outcome added to a debacle of a night for Democrats, who lost the presidency and faced being consigned to minority status on Capitol Hill for years to come.

Republicans celebrated their wins, already looking ahead to midterms in 2018 when Democrats could see their numbers reduced even further with a group of red-state Senate Democrats on the ballot.

Senate Majority Leader Mitch McConnell of Kentucky, who will serve in that role next year under a President Trump, issued a statement congratulating the president-elect.

“After eight years of the Obama administration, the American people have chosen a new direction for our nation. President-elect Trump has a significant opportunity to bring our nation together,” McConnell said. “It is my hope and intent that we succeed in the years ahead by working together with our colleagues across the aisle to strengthen our national and economic security.”

As the night wore on, Democratic operatives struggled to explain why their optimistic assessments of retaking Senate control were so mistaken. Some blamed unexpected turnout by certain segments of white voters, or FBI Director James Comey’s bombshell announcement that he was reviewing a new batch of emails connected with Democrat Hillary Clinton.

In Pennsylvania, GOP Sen. Pat Toomey won a narrow victory for his second term over Democratic challenger Katie McGinty. It was a race Democrats expected to win going into the night — and one that many Republicans felt nearly as sure they’d lose.

The story was the same in Wisconsin, where GOP Sen. Ron Johnson, written off for months by his own party, won re-election against former Democratic Sen. Russ Feingold in a rematch.

In Missouri and North Carolina, where entrenched GOP incumbents Roy Blunt and Richard Burr faced unexpectedly strong challenges from Democrats, both prevailed in the end.

Democrats did grab a Republican-held seat in Illinois, where GOP Sen. Mark Kirk lost to Democratic Rep. Tammy Duckworth, a double-amputee Iraq war vet.