WASHINGTON >> Republicans have taken control of the U.S. Senate and are fighting to keep their majority in the U.S. House, which would produce a full sweep of GOP power in Congress alongside President-elect Donald Trump in the White House.

A unified Republican grip on Washington would set the course for Trump’s agenda. Or if Democrats wrest control of the House, it would provide an almost certain backstop, with veto power over the White House.

Trump, speaking early Wednesday at his election night party in Florida, said the results delivered an “unprecedented and powerful mandate” for Republicans.

He called the Senate rout “incredible.” And he praised House Speaker Mike Johnson, who dashed from his own party in Louisiana to join Trump. “He’s doing a terrific job,” Trump said.

From the U.S. Capitol, Senate GOP Leader Mitch McConnell, privately a harsh Trump critic, called it a “hell of a good day.”

Vote counting in some races could go on for days, and control of the House is too early to call.

The rally for Republicans started in West Virginia, when Jim Justice, the state’s wealthy governor, flipped the seat held by retiring Sen. Joe Manchin. From there, the Republicans marched alongside Trump across the Senate map.

Republicans toppled Democrat Sen. Sherrod Brown in Ohio, the first incumbent senator to fall, with GOP luxury car dealer and blockchain entrepreneur Bernie Moreno. They chased Democrats in the “blue wall” states of Pennsylvania, Michigan and Wisconsin, where Vice President Kamala Harris strained to carry the party forward, though Democrats avoided a total wipeout as Elissa Slotkin won an open Senate seat in Michigan and Sen. Tammy Baldwin was reelected in Wisconsin.

Democratic efforts to oust firebrand Republicans Ted Cruz of Texas and Rick Scott of Florida collapsed. The unexpected battleground of Nebraska pushed Republicans over the top. Incumbent GOP Sen. Deb Fischer brushed back a surprisingly strong challenge from independent newcomer Dan Osborn.

All told, Senate Republicans have a chance to scoop up a few more seats, potentially delivering their most robust majority in years — a coda to outgoing GOP Leader McConnell, who made a career charting a path to power, this time by recruiting high-wealth Republicans aligned with Trump.

The fight for control of the House became a state-by-state slog, much of which unfolded far from the presidential race.

House races are focused in New York and California, where Democrats are trying to claw back some of the 10 or so seats where Republicans have made surprising gains in recent years.

Other House races are scattered around the country, with some of the most contentious in Maine, the “blue dot” around Omaha, Nebraska, and in Alaska.

Democratic House Minority Leader Hakeem Jeffries said the House “remains very much in play.”

To gain control of the House, Democrats need to flip four seats from Republicans, while holding all of their own, a tall task especially in congressional districts where Trump has won.