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 delivered big for Senate 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.) on Election Day, helping Republicans defeat at least three Democratic incumbents in Indiana, Missouri and North Dakota.

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 (D-Ind.), 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 (D-Mo.) and 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 (D-N.D.) conceded relatively early in the evening.

A fourth Democratic senator whom Trump campaigned against, 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.), was on the cusp of losing early Wednesday morning as he trailed by 50,000 votes, or 0.6 percent, with 99 percent of precincts reporting.

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A fifth Democrat, 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.), whom Trump made a top target because of his role in a clash over the Veteran Affairs Department earlier this year, was behind his opponent, Matt Rosendale, early Wednesday by nearly 2 points — or 7,000 votes — with 80 percent of precincts reporting.

McConnell spoke to Trump earlier Tuesday evening to thank him for all the work he did to buck up Senate GOP races, crisscrossing the nation in the final weeks before Election Day to rally the GOP base.

Senate Democrats managed to pare the GOP gains later in the evening by defeating 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-Nev.), their top target.

They also could win the Arizona seat held by retiring Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (R), although the race between Reps. Kyrsten Sinema (D) and 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) was too close to call as of 4 a.m. Wednesday.

Trump hailed Election Day as a “tremendous success” on Twitter, even though Democrats picked up at least 26 House seats and control of the lower chamber.

Senate Republicans are likely to pick up at least two seats and as many as four, depending on how the undecided races in Arizona, Florida and Montana shake out.

As a result, McConnell could lead a Senate Republican majority of between 53 and 55 seats.

There is an outside chance that all the undecided races break for Democrats, which would limit the Senate GOP majority in 2019 to 52 seats.

The expanded GOP majority will make it more difficult for Democrats to recapture the Senate in 2020, when the electoral map will be more favorable for them.

The president on Tuesday evening tweeted a quote from conservative commentator and actor Ben Stein citing a statistic that the party of a sitting president has won seats in the Senate only five times in the past 105 years during a midterm election.

Trump claimed victory after focusing on Senate races in the final month of the campaign and largely ignoring House contests, many of which were fought on more favorable Democratic territory carried by 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.

He traveled extensively in the past week, visiting Florida to campaign for Rick Scott (R) on Halloween, Missouri to rally voters for Josh Hawley (R) on Nov. 1, Indiana to help Mike Braun (R) on Nov. 2, back to Florida on Nov. 3, then to Bozeman, Mont., to boost Rosendale that same day, to Tennessee on Nov. 4 and Indiana on Nov. 5.

At each of his rallies, Trump urged voters to elect a Republican to the Senate, arguing he needed more GOP votes in the upper chamber to pass his agenda and warning that Democrats would hurt the economy if they won back power.

He told supporters who waited for hours Saturday to hear him speak outside of Bozeman that Tester would be in “lockstep” with House Democratic Leader Nancy Pelosi Nancy PelosiPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare House lawmakers reach deal to avert shutdown Centrist Democrats 'strongly considering' discharge petition on GOP PPP bill MORE (Calif.), Rep. Maxine Waters Maxine Moore WatersPowell, Mnuchin stress limits of current emergency lending programs Pelosi: House will stay in session until agreement is reached on coronavirus relief Omar invokes father's death from coronavirus in reaction to Woodward book MORE (D-Calif.) and “Crying Chuck Schumer Chuck SchumerSenate Democrats introduce legislation to probe politicization of pandemic response Schumer interrupted during live briefing by heckler: 'Stop lying to the people' Jacobin editor: Primarying Schumer would force him to fight Trump's SCOTUS nominee MORE,” referring to the Senate Democratic leader from New York.

“Remember, Tester voted against your tax cuts,” he said.

On Monday in Indiana, he attacked Donnelly as a faux conservative who would largely stick with Democratic leaders on key votes.

“All of the sudden, he’s talking about what we’ve been talking about,” he told a rally in Fort Wayne. “Here’s the problem. There’s one problem. We’ll have the election tomorrow and on Wednesday he’ll be totally against us. He’ll never vote for us.”

Every Senate Republican candidate Trump visited in the past week either won or was poised to win at 5 a.m. Wednesday morning.

Trump visited Indiana and Missouri a total of five times each and Montana four times in 2018. He visited North Dakota twice and Florida more than a dozen times this year.

As happened in 2016, public polls underestimated Trump’s influence in battleground states.

Polls showed Nelson, Tester and Donnelly clinging to narrow leads and McCaskill tied with Hawley in the days before the election.

Donnelly and McCaskill ended up losing by 10 and 6 percentage points, respectively, and Nelson and Tester stayed stuck behind in the undecided races as Wednesday morning wore on.

A recount in Florida will be triggered automatically if the margin of victory in the Senate race is less than 0.5 percentage points.

Senate Republican leaders knew months ago that Trump would be crucial to revving up the conservative base in a year when Democrats appeared to have an early advantage in voter enthusiasm.

GOP leaders declined to pick a fight with Trump over trade policy by moving legislation curbing his ability to implement tariffs because they feared it would be counterproductive politically in an election year.

Trump’s success in rallying Republican voters will likely strengthen his hand in the Senate GOP conference in the post-election, lame-duck session and the new 116th Congress, which convenes in January.

Two of the president’s most outspoken Senate Republican critics, Jeff Flake (Ariz.) and Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (Tenn.), are due to retire at the beginning of next year.