Indiana state Treasurer Richard Mourdock defeated Sen. Dick Lugar in Tuesday’s Republican primary in Indiana, ending the career of the longest-serving Republican senator and putting the seat in play for Democrats in the fall.

NBC News projected Mourdock's victory about 20 minutes after the polls closed. He will face Rep. Joe Donnelly Joseph (Joe) Simon DonnellyThe Hill's Morning Report - Sponsored by JobsOhio - Showdown: Trump-Biden debate likely to be nasty Senate Democrats want to avoid Kavanaugh 2.0 Trump taps Amy Coney Barrett for Supreme Court, setting up confirmation sprint MORE, a centrist Democrat, in the general election.

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An emotional Mourdock cheered as his wife was presented flowers and choked up as he recounted how voters had told him they'd pray for him.

Quoting Ronald Reagan and Abraham Lincoln in his victory speech, Mourdock promised he would not only "move the Senate to a more conservative place, but much more than that ... move this country to a better place."

"The supporters of Barack Obama Barack Hussein ObamaIt's now up to health systems to solve our food problems Testing the Electoral College process against judicial overreach Obama steps into The Shade Room to urge 'roommates' to vote, says White House 'working to keep people from voting' MORE are not going to win," he said, his voice rising. "Mr. Donnelly has been close to Barack Obama for the last several years. We're going to make that record clear and it's not going to be accepted by the voters of Indiana in November."

In a statement to supporters, Mourdock thanked Lugar, saying he was "grateful" for Lugar's 35 years of service.

Lugar thanked his family and supporters during his concession speech, and promised to continue to work on national security issues in his final months in Congress as well as push for a farm bill. "My public service is not concluded," he said.

Lugar also said he hopes Mourdock "prevails" over Donnelly in the general election.

Republicans moved quickly to back Mourdock in the general election. Mourdock said the first call he'd received after he won was from Cornyn promising the NRSC would invest heavily in the race. Sen. Jim DeMint's (R-S.C.) Senate Conservatives Fund sent out an email Tuesday night asking his supporters to donate to Mourdock.

The White House put out a statement praising Lugar, an unusual move for a member of the opposing party, showing how well-liked Lugar was on both sides of the aisle within Washington.

"As a friend and former colleague, I want to express my deep appreciation for Dick Lugar’s distinguished service in the United States Senate," President Obama said in the statement. "While Dick and I didn’t always agree on everything, I found during my time in the Senate that he was often willing to reach across the aisle and get things done... Senator Lugar comes from a tradition of strong, bipartisan leadership on national security that helped us prevail in the Cold War and sustain American leadership ever since."

Lugar, a six-term senator first elected in 1976, was the top target for national conservative groups, including the fiscally conservative Club for Growth, the National Rifle Association and the Tea Party-affiliated FreedomWorks. Together, they spent more than $3 million against Lugar, double the amount Mourdock raised and spent on the race.

Many blamed Lugar’s weak campaign as much as the onslaught of outside spending for his loss. A number of GOP strategists friendly to Lugar were frustrated that the senator failed to take Mourdock seriously until it was too late, and argued that if he’d focused on renewing relationships with local party activists early on, he could have avoided a challenge.

“It's unclear if he was in shape for any kind of campaign or fully cognizant of the challenge that awaited him, if he had a real strategy and whether it was efficiently executed,” said Ed Feigenbaum, the editor of the nonpartisan political newsletter Indiana Legislative Insight. “This was a referendum on Richard Lugar. It could have been him against ‘none of the above’ [an uncontested race].”

Conservatives in Indiana and Washington, D.C., were angered by Lugar’s support of the Troubled Asset Relief Program that bailed out Wall Street, votes in favor of President Obama’s Supreme Court justices and other political positions anathema to hardliners.

The Club for Growth was the biggest player against Lugar — they spent a whopping $1.5 million against him and helped Mourdock raise an additional $300,000, a significant portion of his campaign funds.

Club for Growth President Chris Chocola called Mourdock’s win a “historic victory” before thanking Lugar for his service.

“Richard Mourdock defeated a legend in Indiana politics because of his hard work, focus on the issues, and his conservative message,” he said.

Mourdock’s win is a much-needed boost to the Tea Party movement, which was disappointed that Mitt Romney won the GOP presidential nomination instead of a more fiscally conservative candidate. The conservative grassroots movement has far fewer opportunities this year than it did in 2010 to make a statement by beating a well-known centrist Republican.

Another problem for Lugar was how little time he spent in Indiana the last few years. Lugar has lived in Washington, D.C.’s suburbs for decades, and a residency battle stirred up by Indiana Democrats and outside groups drew much attention to that fact. Three-quarters of Indiana’s Republican county chairmen endorsed Mourdock shortly after he jumped into the race, a sign of how out of touch Lugar had grown with local activists.

Lugar, the longtime Senate Foreign Relations ranking member, also refused to back away or apologize for unpopular positions, and instead of hiring top Republican strategists to win the race he sent out a number of longtime Capitol Hill staffers with little campaign experience to run his reelection bid.

While Mourdock struggled early on with fundraising, he held his own against Lugar — outworking him on the ground and avoiding making any mistakes in a debate that focused largely on foreign policy.

He will now face Donnelly, a recruit Democrats are high on. Donnelly held onto his Republican-leaning House seat in the GOP wave year of 2010. The three-term lawmaker has the right profile for an Indiana Democrat: anti-abortion rights, pro-gun rights and relatively fiscally conservative.

Republicans have long maintained Donnelly can’t win in the GOP-leaning state, pointing to his weak fundraising numbers and his vote for Democrats’ health law. They also point to Sen. Dan Coats Daniel (Dan) Ray CoatsFBI chief says Russia is trying to interfere in election to undermine Biden The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump, Biden renew push for Latino support Former Intel chief had 'deep suspicions' that Putin 'had something on Trump': book MORE’s (R-Ind.) 15-point win in 2010 over former Rep. Brad Ellsworth (Ind.), a Democrat with a similarly centrist profile.

But Democrats strongly disagree and argue the seat is now in play, which could help the party keep control of the upper chamber.

On Tuesday the Democratic Senatorial Campaign Committee began a barrage of attacks against Mourdock, blasting him for questioning the constitutionality of Medicare and Social Security, ripping him for spending $2 million in state funds on a lawsuit challenging the federal government-backed bankruptcy of Chrysler and his calling the lawsuit his “Rosa Parks moment.”

Updated at 9:30 p.m.