Joe Donnelly concedes to Mike Braun in Indiana Senate race

Democratic Sen. Joe Donnelly has conceded to Republican Mike Braun in the race for Indiana’s U.S. Senate seat.

"A few minutes ago, I called Mike Braun and congratulated him on winning a hard-fought race. I’d like to thank every single American who believed in this campaign and worked to make it successful, and every Hoosier whom I have come across over the last six years who helped me to better serve my state," Donnelly said in a statement. "It has been one of the greatest honors of my life to represent Indiana in the Senate. I wish Mike the best, and I hope he makes every single Hoosier proud as our senator."

ABC News has also projected Braun's victory based on an analysis of the vote.

A former state representative, Braun ran as a staunch supporter of President Donald Trump’s agenda, often criticizing Donnelly for not supporting the president enough — including for his vote against the confirmation of Supreme Court Justice Brett Kavanaugh. Braun’s victory is key for Republicans in their effort to keep control of the Senate.

Preliminary exit poll results indicate President Trump has a 52-48 percent approval/disapproval rating in Indiana, where he won by 19 percentage points in 2016. Indiana native Mike Pence fares better at a 54-43 favorability rating. Thirty percent say they’re voting to show support for Trump, 34 percent to oppose him and 32 percent say he’s not a factor. Brett Kavanaugh played a major role in the vote of a majority of voters, as 53 percent of voters say Sen. Joe Donnelly's vote against Kavanaugh was important to their vote.

Indiana is a state President Trump won by nearly 20 points in 2016 — meaning incumbent Sen. Joe Donnelly had an uphill battle in an ultimately unsuccessful re-election bid.

There were also briefly election issues at the polls in one Indiana County. Johnson County, a midsize county about 22 miles south of Indianapolis, reported issues with its electronic poll books, which contributed to longer lines, but noted that the issues were sincerely resolved.

This year’s Indiana Senate race featured showdowns in the primary and general election cycles, putting Vice President Mike Pence’s home state in the spotlight for battles within his own party, as well as across the aisle.

In May, Indiana businessman and former State Representative Mike Braun won the GOP primary election, edging out House Reps. Todd Rokita and Luke Messer. The primary was filled with personal jabs and created an intra-party divide between sitting lawmakers and a relative political outsider. That difference in approach to politics spoke to a larger theme facing the Republican Party heading into November’s election.

Republican voters in the Hoosier State flocked to a Washington outsider during the 2016 presidential campaign, but after taking down a pair of congressmen in the primary, it appears Braun's statehouse experience and his policy stances helped push him past the moderate Donnelly.

While Donnelly aligned with Republicans on issues like abortion, he had a target on his back for voting against the tax reform bill spearheaded by President Trump. The president directly targeted Donnelly during a tax event last fall in Indianapolis.

“If Senator Donnelly doesn't approve it, because you know, he's on the other side, we will come here. We will campaign against him like you wouldn't believe,” Trump said at the time.

The president made two stops in Indiana on Braun's behalf during the final week of the campaign. On Friday, both the president and vice president campaigned in Indianapolis for Braun, as did former Indiana Hoosiers basketball coach Bob Knight. The president made a second stop in Fort Wayne on Monday to stump for Braun one more time before Election Day.

On the Democratic side, former President Barack Obama visited Indiana to stump for Donnelly on Sunday and praised the senator for his bipartisanship.

"Joe Donnelly and I didn't agree all the time. But Joe always let me know where he stood and I knew what he believed in and that he always was focused on, 'What's the best thing for the Hoosiers that he served?'" Obama said. "He was honest and he was direct. So you can count on that. That's what you want. You don't want just a yes man all the time."

Health care was the top issue of four major issues polled, with 42 percent of voters saying it was the top issue facing the country. Hoosier State voters give Democrats a 50-44 advantage on the question of who will better protect pre-existing condition coverage. Immigration was only the top issue for 26 percent of voters, despite President Trump's push on the issue. More say that his immigration policies are "too tough" (41 percent) than "about right" (34 percent) or "not tough enough" (21 percent). Despite the less-than-ideal exit poll numbers on the issues for Republicans, it appears they have been able to pull out a key flip of a Senate seat.

If the race were closer, it could have been complicated by the candidacy of a third-party candidate, Libertarian Lucy Brenton. The Libertarian nominee may earn enough votes to swing the election. Donnelly’s campaign has been tied to ads touting Brenton as “the true anti-tax conservative” in an effort to peel off conservative votes from Braun. President Trump slammed Donnelly in a tweet Saturday accusing the first-term Democrat of “trying to steal the election.”