Businessman Mike Braun has won the Indiana GOP primary, vanquishing two sitting congressmen in what became one of the nastiest primaries in the country.

Braun sought every opportunity to frame himself as the outsider in the race, dismissing Rokita and Messer as two Washington insiders. The two congressmen spent most of the race taking shots at each other — a dynamic that may have given Braun the space he needed to win. As Republicans optimistically eye a pickup opportunity, Democrats are hopeful they can build on the GOP primary fight to launch more attacks on Braun before November. Networks called the race for Braun not long after 8 p.m. and he continued to hold on to the lead with about 40 percent throughout the night. Indicative of the furious battle between the two congressmen, Rokita and Messer were separated by only a few tenths of a percentage point.

For months, the Indiana primary appeared to be a race between Rokita and Messer, two former college classmates locked in a bitter feud. The two men began saber-rattling before they officially jumped in, accusing each other of planting negative stories in the press and warning the other against running.

But while Braun initially laid low, he began to kick his campaign into gear over the winter. He loaned his campaign millions of dollars, jumping on the television airwaves first and beginning to carve out a space as an alternative to the warring congressmen.

As Braun began to move up in the polls, he became a more frequent target of attacks. The two congressmen sometimes doubled up on him during debates, pointing to his past votes in Democratic primaries and to raise taxes while in the state House.

Braun spent much of his victory speech on a call for unity after the rough primary.

"When it comes to Luke Messer and Todd Rokita, it was a difficult decision for many because we were all good conservatives. Sometimes it gets a little difficult to differentiate. In the process of doing it, it can get intense, it can get harsh," he said as he addressed supporters Tuesday evening. "But I hope they will join me, like I would with them, yes, because now, our common goal all along was to retire Joe Donnelly.”

In Braun, the GOP now has a candidate around which to unite — not to mention one worth between $37 million and $95 million who has already shown the willingness to self-fund. That dynamic could be important ahead of a costly general election, especially since the party doesn’t have to worry about its candidate refilling its coffers to retool for the general election.

"Hoosiers do not look to government first to solve the problems and Hoosiers, just like businesses, just like families, just like local government and just like our state government, we live within our means and still accomplish great things," he said.

"His record is going to be easy to flush out and we intend to do that and be the individual that makes the case not only for what we believe in but also to send Joe Donnelly to an early retirement."

But as the nasty primary came to a close, it dredged up damaging stories about all three candidates, including Braun. In the GOP nominee's case, an early May Associated Press story headlined “Senate candidate Mike Braun's rhetoric, business record don't line up.” The piece noted his business’s reliance on importing goods, which could complicate the GOP’s attacks on Donnelly as “Mexico Joe” for his family business’s use of Mexican labor.

Democrats have made clear that they are ready to pounce on that record and on many of the other attacks on him that surfaced during the primary. And they've brushed aside Republicans like Braun labeling Donnelly as partisan by pointing to nonpartisan rankings that show him as one of the more bipartisan senators in office.

Outside of the pivotal general election, the victory also deals a heavy electoral setback to Rokita and Messer, who are now lame ducks in the House. With primaries for their seats also decided Tuesday , the two members will be out of a job come January, but could opt to run again in 2020.

Updated: 9:42 p.m.