Senate Republicans expanded their 51-seat majority on Tuesday, overcoming historic political headwinds that cost their party the House.

The results in key battleground races mark a major victory for the caucus and Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) and will provide President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE with a GOP firewall in Congress as emboldened House Democrats are itching to launch new investigations into the administration.

ADVERTISEMENT

Republicans quickly dashed any Democratic hopes of flipping the Senate by defeating two red-state incumbents and holding onto Sen. Ted Cruz Rafael (Ted) Edward CruzTrump argues full Supreme Court needed to settle potential election disputes Press: Notorious RBG vs Notorious GOP The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE’s seat in Texas. By early Wednesday, they had toppled Democratic Sens. Joe Donnelly Joseph (Joe) Simon DonnellyTrump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court Momentum growing among Republicans for Supreme Court vote before Election Day MORE (Ind.), Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE (N.D.) and Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (Mo.).

They also appeared poised to pick up Florida, though a spokesman for Sen. Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D-Fla.) said Wednesday morning that the three-term senator had not conceded to Gov. Rick Scott (R).

“Based on numerous media reports the U.S. Senate race has been called for Rick Scott. This obviously is not the result Senator Nelson and his campaign had worked so hard for. The Senator will be making a full statement tomorrow to thank all those who rallied to our cause,” Nelson's campaign said in a statement.

In addition to preventing an upset in Texas, Republicans held onto retiring Sen. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE’s seat in Tennessee, with Rep. Marsha Blackburn Marsha BlackburnTaylor Swift on National Voter Registration Day: 'We need everyone' Democrats smell blood with new DHS whistleblower complaint Hillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections MORE (R-Tenn.) easily defeating former Gov. Phil Bredesen (D).

The end result will give Republicans at least a 52-seat majority starting in January, with the potential to add additional seats in the coming weeks.

A special election in Mississippi is headed to a Nov. 27 runoff between Sen. Cindy Hyde-Smith (R-Miss.), who was appointed to succeed retiring Sen. Thad Cochran William (Thad) Thad CochranEspy wins Mississippi Senate Democratic primary Bottom Line Mike Espy announces Mississippi Senate bid MORE (R-Miss.), and Democratic candidate Mike Espy, a former U.S. Agriculture secretary.

The Arizona Senate race between Reps. Martha McSally Martha Elizabeth McSallyTumultuous court battle upends fight for Senate Grassley, Ernst pledge to 'evaluate' Trump's Supreme Court nominee The Hill's Campaign Report: Biden goes on offense MORE (R-Ariz.) and Kyrsten Sinema (D-Ariz.) is not expected to be called until later this week since more ballots need to be counted to break the statistical tie.

And Sen. Jon Tester Jonathan (Jon) TesterPence seeks to boost Daines in critical Montana Senate race This World Suicide Prevention Day, let's recommit to protecting the lives of our veterans Filibuster fight looms if Democrats retake Senate MORE (D-Mont.), after leading in election results for most of Tuesday night, had fallen behind GOP challenger Matt Rosendale as of 2 a.m. EST on Wednesday.

But even if Democrats win in Arizona, Montana and Mississippi, it won’t be enough to flip control of the Senate. The best possible outcome for Democrats would be a 52-48 Republican majority.

Republican National Committee Chairwoman Ronna Romney McDaniel said Democrats were able to turn a Democratic “tsunami into a ripple.”

"With gains in the Senate, Republicans defied history, an achievement reached only four times in history,” she said, referencing the rarity of the president’s party picking up Senate seats during the first midterm in a presidency.

The GOP’s path to keeping, and even expanding, its Senate majority was aided mightily by a favorable map that saw Republicans defending nine seats compared to 26 for Democrats, 10 of which were in states won by Trump in 2016.

Heitkamp’s race was expected to end up in Republican hands, and a few other seats held by Democrats were locked in a statistical tie heading into Election Day.

As control of the House appeared to fade for Republicans in recent weeks, Trump homed in on Senate races, barnstorming through key states that would determine if Republicans would be able to keep and expand their majority in the chamber.

McConnell and Trump spoke on Tuesday night amid the favorable election results, a spokesman for the Senate GOP leader confirmed, and McConnell thanked the president for his help in picking up seats.

McConnell also took a victory lap on Tuesday night, with his campaign account tweeting a GIF of the GOP leader smiling.

The two men have touted their relationship during the midterm campaign, a stark turnaround from the summer of 2017, when they were locked in a public war of words after the failed ObamaCare vote.

Aside from setting up a competitive Senate fight in 2020, the expanded majority could pay dividends for Republicans starting next year.

Though long-held GOP goals like repealing ObamaCare are off the table with a Democratically controlled House, Republicans will have a smoother path to confirming controversial Trump nominees as senators brace for a massive post-midterm Cabinet shake-up.

"When the GOP maintains control of the Senate, the conservative judicial train is going to keep running!" GOP Sen. Lindsey Graham Lindsey Olin GrahamSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (S.C.), who could be the next Judiciary Committee chairman, said in a tweet.

Several Trump picks have been thwarted by the narrow Senate majority that effectively gives moderate GOP senators the power to make or break their nomination. A larger majority will change that dynamic.

Tuesday wasn’t without some bright spots for Senate Democrats, who worked throughout the cycle to limit their liabilities.

Democratic Sens. Joe Manchin Joseph (Joe) ManchinThe Hill's Morning Report - Sponsored by Facebook - Trump, GOP allies prepare for SCOTUS nomination this week Trump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court MORE (W.Va.), Sherrod Brown Sherrod Campbell BrownSenate Democrats release report alleging Trump admin undermined fair housing policies Bipartisan praise pours in after Ginsburg's death Emboldened Democrats haggle over 2021 agenda MORE (Ohio), Bob Casey Robert (Bob) Patrick CaseySecond GOP senator to quarantine after exposure to coronavirus GAO report finds brokers offered false info on coverage for pre-existing conditions Catholic group launches .7M campaign against Biden targeting swing-state voters MORE Jr. (Pa.), Tammy Baldwin Tammy Suzanne BaldwinKeep teachers in the classroom Cher raised million for Biden campaign at LGBTQ-themed fundraiser Democrats seek balance in backing protests, condemning violence MORE (Wis.) and Debbie Stabenow Deborah (Debbie) Ann StabenowOVERNIGHT ENERGY: Trump rollbacks could add 1.8 billion tons of greenhouse gas emissions over 15 years: analysis | Intensifying natural disasters do little to move needle on climate efforts | Experts warn wildfire smoke could worsen COVID-19 GAO report finds brokers offered false info on coverage for pre-existing conditions Democrats back away from quick reversal of Trump tax cuts MORE (Mich.), each won reelection in states that voted for Trump in 2016.

Democrats also staved off GOP upsets in New Jersey and Minnesota: Sen. Bob Menendez Robert (Bob) MenendezKasie Hunt to host lead-in show for MSNBC's 'Morning Joe' Senators ask for removal of tariffs on EU food, wine, spirits: report VOA visa decision could hobble Venezuela coverage MORE (N.J.) won reelection and Sen. Tina Smith Tina Flint SmithThe Hill's Campaign Report: Trump and Biden vie for Minnesota | Early voting begins in four states | Blue state GOP governors back Susan Collins GOP Senate candidate says Trump, Republicans will surprise in Minnesota Biden promises Democratic senators help in battleground states MORE (Minn.) was elected to serve out the final two years of Al Franken Alan (Al) Stuart FrankenGOP Senate candidate says Trump, Republicans will surprise in Minnesota Peterson faces fight of his career in deep-red Minnesota district Getting tight — the psychology of cancel culture MORE’s Senate term.

And Democrats managed to flip a GOP seat as Rep. Jacky Rosen Jacklyn (Jacky) Sheryl RosenHillicon Valley: Election officials prepare for new Russian interference battle | 'Markeyverse' of online fans helps take down a Kennedy | GOP senators unveil bill to update tech liability protections Google, Apple, eBay to meet virtually with lawmakers for tech group's annual fly-in Senate Democrats demand answers on migrant child trafficking during pandemic MORE (Nev.) ousted Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R), the only Republican running in a state carried by former Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE in 2016. Rosen's victory is a significant bright spot in an otherwise bitter election night for Senate Democrats and comes after the party swept the state in 2016.