Republicans seized control of the U.S. Senate late Tuesday after flipping Democrat-held seats, holding onto GOP incumbents and wresting away the majority that Democrats held since 2020.

The unexpected battleground of Nebraska pushed Republicans over the top, where incumbent GOP Sen. Deb Fischer brushed back a surprisingly strong challenge from independent newcomer Dan Osborn.

Democrats watched their efforts to salvage their slim majority slip out of reach as tallies rolled in across a map that favoured Republicans.

Early in the night, Republicans flipped one seat in West Virginia with the election of Jim Justice, who easily replaced retiring Sen. Joe Manchin. Democrat efforts to oust firebrand Republicans Ted Cruz of Texas and Rick Scott of Florida collapsed.

While Texas hasn't elected a Democrat statewide in almost 30 years, Colin Allred, a Dallas-area congressman and former NFL linebacker, positioned himself as a moderate and leaned into his support for reproductive rights amid the state's abortion ban, which is one of the strictest in the nation.

Cruz's victory came after Democratic efforts to salvage their Senate majority evaporated when Democrat Sen. Sherrod Brown in Ohio lost his re-election to Republican Bernie Moreno, a wealthy Trump-era newcomer.

With control of Congress at stake, the contests for the House and Senate will determine which party holds the majority and the power to boost or block a president's agenda, or if the White House confronts a divided Capitol Hill.

Results still coming in as senators mark historic firsts

Republicans had 51 seats early Wednesday morning, and the Democrats 42. Once the rest of the results come in, the final numbers could have a significant impact on abortion rights and other contentious issues in the U.S.

If the Republicans stay at 51, moderate Republican Lisa Murkowski, who sometimes votes with Democrats, could block anti-abortion judges. However, a bigger majority in the Senate will give Republicans veto power over Harris's judicial picks — and potentially carte blanche to keep confirming Trump's judges — further cementing conservative control over the courts. 

Several states will send history-makers to the Senate.

Voters elected two Black women to the Senate — Democrats Lisa Blunt Rochester of Delaware and Angela Alsobrooks of Maryland. Blunt Rochester won the open seat in her state while Alsobrooks defeated Maryland's popular former governor, Larry Hogan.

Just three Black women have served in the Senate, and never before have two served at the same time.

In New Jersey, Andy Kim became the first Korean American elected to the Senate, defeating Republican businessman Curtis Bashaw. The seat opened when Bob Menendez resigned this year after his federal conviction on bribery charges.

Elsewhere, House candidate Sarah McBride, a Democratic state lawmaker from Delaware who is close to the Biden family, won her race, becoming the first openly transgender person elected to Congress.

One of the most-watched Senate races, in Montana, may be among the last to be decided. Democrat Jon Tester, a popular three-term senator and "dirt farmer," is in the fight of his political career against Trump-backed Tim Sheehy, a wealthy former Navy SEAL who made derogatory comments about Native Americans, a key constituency in the Western state.

Billions of dollars have been spent by the parties, and outside groups, on the narrow battleground for both the 435-member House and 100-member Senate.

Top 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 with star lawmakers who helped deliver the party to power.

Vote counting in some races could extend well past Tuesday.

"We're in striking distance, in terms of taking back the House," House Democratic leader Hakeem Jeffries told The Associated Press during a recent campaign swing through Southern California. Jeffries is in line to make history as the first Black speaker if his party wins control.

But House Speaker Mike Johnson predicts Republicans will keep "and grow" the majority.