Rep. Mike Collins has won the Republican Senate runoff in Georgia, NBC News projects, setting up a race against Democratic Sen. Jon Ossoff in one of the most competitive and important campaigns in the country.

Collins’ primary victory over former college football coach Derek Dooley is also a win for President Donald Trump, who endorsed the two-term congressman just a few days before Tuesday’s runoff election. Dooley, meanwhile, had been endorsed by Republican Gov. Brian Kemp, who campaigned heavily for his candidate and argued the GOP needed a political outsider to defeat Ossoff.

Collins and Dooley met in the runoff after no candidate won a majority of the primary vote on May 19. As Republicans continued to battle for the nomination, Ossoff has been gearing up for a hotly contested race. He is the only Democratic senator running for re-election in a state Trump carried in 2024, and Georgia is a must-win state for Democrats, who are trying for a net gain of four seats to take over the Senate.

First elected to the House in 2022, Collins has pitched himself as a staunch Trump ally, saying in a recent debate that he is a “conservative work horse.” And he has already started to lay out his case against Ossoff, who was elected to the Senate in a runoff following the 2020 election.

Ossoff “doesn’t represent us, he doesn’t reflect our state and represent the people or our values,” Collins said at a rally in Cumming, Georgia, on the eve of the primary runoff. He went on to say that Ossoff “has never had a real job in his life” and “is bought and paid for by those crazy folks in California and nut jobs in New York.”

The senator has also begun to make his case against Collins, saying at a recent rally that Collins is “a congressman who’s only a congressman because his daddy was a congressman.”

Collins has been a vocal Trump supporter, often noting on the campaign trail and on the airwaves that he authored the Laken Riley Act, an immigration detention measure that was the first bill Trump signed into law in his second term. The bill was named after a Georgia nursing student who was killed by a Venezuelan man who entered the U.S. illegally, and the legislation drew some bipartisan support, including from Ossoff.

Collins represents a deeply Republican district and is an ardent conservative who has stuck close to the president. Asked after a campaign event last month if he disagreed with any of Trump’s actions in his second term, Collins told NBC News that he disagrees with Trump on the hours of sleep needed to function, noting the president does not get much sleep.

“Listen, I ran on Trump policies. I ran on America first. I know what those policies did and can do for this country and for the people of this country. That’s what I’m running with, and he is — I wholeheartedly support what he’s been doing,” Collins said at the time.

His support for Trump and his policies comes as voters have been voicing concerns about Trump’s handling of the economy and high costs. Asked about those concerns after his Monday night rally, Collins suggested the economy would turn around.

“Well, you know, it looks like the Iran deal is done,” Collins said, referring to an agreement to end the war with Iran, which has contributed to high gas prices.

“The economy is moving,” Collins later added. “Gas prices are too high, but you’re going to see them start coming down awful soon.”

Ossoff, meanwhile, also previewed at his rally that he will highlight a House Ethics Committee probe into whether Collins misused congressional funds by paying a former aide for campaign work and by employing that aide’s girlfriend, who did not do work for the office. Collins has said the allegations are “bogus.”

The aide, Collins’ former chief of staff Brandon Phillips, was let go from the campaign and his congressional office after publishing a disparaging post on behalf of Collins’ campaign account on X.

A Collins supporter pressed the congressman during his Monday rally on how he plans to respond to issues that had been “all over the ads,” referring to attacks from Dooley and his allies highlighting the ethics probe and Phillips controversies.

“I can win this thing. They can sling whatever they want, you know. I can’t help that,” Collins said, later adding that “our real enemy is Jon Ossoff.”

And although the primary with Dooley had gotten negative, Collins was confident that Republicans would unite after the runoff.

“Republicans have always had spirited primaries. We always will. But at the end of the day, you always see that we unite together and we march lockstep, because we all have the same mission,” Collins said. “And that is to make sure that we put a Republican in that US Senate seat.”

The Georgia Senate race is going to be a tough — and expensive — battle for both parties.

The Peach State has emerged as a closely contested battleground in recent years. Trump won Georgia by just two points last year. In 2020, Joe Biden won Georgia by less than half a percentage point. Ossoff won his seat in January 2021 by just over 1 point, defeating then-GOP Sen. David Perdue in a runoff and handing Democrats the Senate majority that year.

The two major super PACs involved in Senate races have already pledged to spend a combined $64 million on the race, and that spending could continue to balloon as the contest heats up.

On the candidate level, Ossoff starts the race with an overwhelming financial advantage. His campaign has raised more than $80 million so far and had $32 million to spend as of April 29, when he filed his most recent campaign finance report.

Collins, whose campaign had to file a fundraising report more recently due to the runoff, has raised $4.9 million so far and had $1.2 million in his campaign account as of May 27.

And Ossoff has expressed confidence that he’ll win in November, regardless of his Republican opponent.

“It doesn’t matter which one wins,” Ossoff said at a recent rally, referring to the GOP runoff. “They’re both corrupt political insiders and they’re both pro-war, pro-tariff and pro-cutting your health care. They’re both Trump puppets, and we’ll beat either one of them in November.”