GOP to retain Senate majority

Republicans are guaranteed to keep control of the Senate after netting early victories by flipping four Democratic seats and winning a marquee race in Texas.

GOP candidates scored major victories in Indiana, Missouri and North Dakota, while several other toss-up races remain too close to call, paving the way for the party to potentially expand its 51-49 majority.

Businessman Mike Braun (R) unseated Sen. Joe Donnelly (D-Ind.) — marking the first red-state Democrat to lose on Tuesday and giving the GOP an early seat flip.

Three more Democrats followed: Sens. Heidi HeitkampMary (Heidi) Kathryn HeitkampRed dresses displayed around American Indian museum to memorialize missing, murdered native women Lobbying World Lobbying World MORE (N.D.), Claire McCaskillClaire Conner McCaskillLobbying world Dem candidate has Hawley served subpoena at CPAC Annual scorecard ranks GOP environmental efforts far below Dems in 2018 MORE (Mo.) and Bill NelsonClarence (Bill) William NelsonEx-House Intel chair: Intel panel is wrong forum to investigate Trump's finances The Hill's Morning Report - Trump budget reignites border security fight 2020 party politics in Puerto Rico MORE (Fla.).

The red-state Democratic losses came after Republicans avoided a major upset in Texas, where Rep. Beto O'RourkeRobert (Beto) Francis O'RourkeThe Hill's Morning Report - Presented by Pass USMCA Coalition - Mueller report is huge win for President Trump Biden, Sanders edge Trump in hypothetical 2020 matchups in Fox News poll Here's what the Dem candidates for president said about the Mueller report MORE (D) shot into an early lead but was ultimately unable to overcome Sen. Ted CruzRafael (Ted) Edward CruzNunes on Mueller report: 'We can just burn it up' 18 state attorneys general call on Justice Dept to release Mueller report Lawmakers clash over whether conclusion of Mueller investigation signals no collusion MORE (R).

Absent a last-minute upset in a seat controlled by Republicans, the three Democratic losses and the GOP win in Texas guarantees Republicans will hold onto the chamber, even with undecided races in Arizona and Nevada.

Democrats entered Election Day looking to defend seats in 10 states that Trump won in 2016, presenting them with an uphill battle to take back the Senate or maintain the GOP's slim majority.

Sen. Jon Tester (Mont.) is the last vulnerable Democrat whose race has yet to be called. Though he remains in the lead against GOP challenger Matt Rosendale, the race has tightened as more precincts have begun reporting.

One race that will not be decided on Tuesday is a special election in Mississippi, where Sen. Cindy Hyde-Smith (R) was hoping to prevent a runoff election for her Senate seat.

Hyde-Smith and Democrat Mike Espy, as the top two candidates, will advance to a Nov. 27 runoff, but the outcome of that race will not determine control of the Senate.

Even with the Mississippi race undecided, Democrats could sweep the remaining battleground states and fall short, with Republicans holding a 52-47 majority in that scenario.

If Democrats sweep the remaining battleground states and Republicans ultimately win Mississippi, where Trump remains popular, that would give Republicans a 53-47 majority.

Democrats have gotten some good news on Tuesday night. Sen. Joe ManchinJoseph (Joe) ManchinSenate gears up for Green New Deal vote Overnight Energy: Green New Deal vote set to test Dem unity | Renewables on track to phase out coal, study finds | EPA chief reportedly recuses himself from mine review Green New Deal vote tests Dem unity in Senate MORE (D-W.Va.) held off state Attorney General Patrick Morrisey in what was expected to be a competitive race.

Meanwhile, Sen. Tim KaineTimothy (Tim) Michael KaineWhy do so many Democrats embrace hate speech? Dem senator wants Trump to extend immigration protections to Venezuelans Pentagon sends Congress list of projects that could lose funds to Trump's emergency declaration MORE (D-Va.) and Sherrod BrownSherrod Campbell BrownGreen New Deal vote tests Dem unity in Senate Trump mounts Rust Belt defense Warren, Klobuchar call on FTC to curtail use of non-compete clauses MORE (D-Ohio) easily won reelection, and voters in New Jersey decided to send Sen. Bob MenendezRobert (Bob) MenendezThe Hill's 12:30 Report: Manafort sentenced to total of 7.5 years in prison Acting Defense chief calls Graham an 'ally' after tense exchange William Barr is right man for the times MORE back to Washington for another six-year term.

But the defeat in Texas comes after Tennessee, another potential pickup, was quickly taken out of reach for Democrats with Rep. Marsha BlackburnMarsha BlackburnTaylor Swift says she wants to get more involved in politics Bipartisan lawmakers introduce resolution supporting vaccines Hillicon Valley: Cohen stuns Washington with testimony | Claims Trump knew Stone spoke to WikiLeaks | Stone, WikiLeaks deny | TikTok gets record fine | Senators take on tech over privacy MORE (R-Tenn.) defeating former Gov. Phil Bredesen (D) after holding a lead in the polls heading into Tuesday.

Democrats are still eyeing potential pick-ups in two western states with seats currently held by Republicans — Arizona and Nevada.

Rep. Kyrsten Sinema (D-Ariz.) had a slight lead over Rep. Martha McSallyMartha Elizabeth McSallyArpaio's wife recovering after rattlesnake bite in Arizona Former astronaut running for Senate in Arizona returns money from paid speech in UAE The Hill's Morning Report — Washington readies for Mueller end game MORE (R-Ariz.) heading into Tuesday as they battle to succeed retiring Sen. Jeff FlakeJeffrey (Jeff) Lane FlakeTrump's attacks on McCain exacerbate tensions with Senate GOP Schumer to introduce bill naming Senate office building after McCain amid Trump uproar Trump keeps tight grip on GOP MORE (R). If Sinema is victorious it would be the first time since 1988 that Arizonans have elected a Democrat to the Senate.

Meanwhile, Democrats held a lead among early voters in Nevada, where Democrats are feeling bullish about their ability to unseat Sen. Dean HellerDean Arthur HellerTrump suggests Heller lost reelection bid because he was 'hostile' during 2016 presidential campaign Trump picks ex-oil lobbyist David Bernhardt for Interior secretary Oregon Dem top recipient of 2018 marijuana industry money, study finds MORE (R-Nev.), the only Republican senator up for reelection in a state won by Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonGraham: McCain 'acted appropriately' by handing Steele dossier to FBI Why Mueller's hedge on obstruction decision was a mistake Giuliani says news media treat Dems better than GOP MORE in 2016.

Updated at 12:54 a.m.