Republicans will hold their majority in the US House of Representatives as expected, networks projected Tuesday, and appeared increasingly likely to maintain their grip on the Senate, where the battle for control is tighter.
With the US election in full swing, the party of populist presidential candidate Donald Trump was on track to take 235 seats to the Democrats' 200, according to NBC's House model.
That would be a 12-seat gain for Democrats, but still far short of what would be necessary to snatch the chamber back from Republican control.
By holding the House, Republicans secure a policy check on Hillary Clinton in the event she wins the presidency.
And, if Trump wins, it will be far easier for the chief executive to push through legislation.
The Senate, where 34 of the 100 seats are in play Tuesday, is also in Republican hands. It had been under far sharper threat of a Democratic takeover, but a strong showing by Trump at the top of the ballot appeared to be lifting the fortunes of several Republican incumbents whose re-elections are in jeopardy.
With that chamber currently 54 to 46 in the GOP's favor, Democrats need to gain five seats for a clean majority. But the New York Times forecast unit gave Democrats just a five percent chance of reaching that goal.
In the event the Senate is 50-50, control goes to the party that wins the White House, because the US vice president holds a deciding vote in the event of a tie.
Democrats claimed a quick pick up Tuesday in Illinois, where two-term congresswoman Tammy Duckworth, an Iraq war veteran who lost her legs when the Black Hawk helicopter she was co-piloting was shot down there, defeated incumbent Senator Mark Kirk.
"Thank you for making me the next senator from Illinois," Duckworth said in a tweet. "This victory would not have been possible without your support."
But Republicans bolstered their chances to hold the upper chamber when three of the party's lawmakers fought off spirited challenges.
Senator Marco Rubio kept his seat in Florida, as did incumbent Richard Burr in North Carolina, while congressman Todd Young of Indiana denied a former senator, Evan Bayh, from reclaiming his old seat.
Rubio had been a rapidly rising GOP star until he challenged Trump for the Republican primary and got swept aside. He had said he would leave Congress, but changed his mind earlier this year and mounted a strong comeback.
In a victory speech before jubilant supporters in Miami, Rubio sought to soothe heated tempers and appeal to Americans of all stripes after a toxic 18-month presidential campaign overwhelmed by rhetoric, accusations of racism and xenophobia, and anger on both sides.
"While we can disagree on issues we cannot share a country where people hate each other because of their political affiliations," Rubio, 45, said.
"I hope that I and my colleagues as we return to work in Washington, DC can set a better example of how political discourse should exist in this country."
A handful of other Senate races with Republican incumbents, in states like New Hampshire, Pennsylvania and Wisconsin are considered tossups.