COLUMBUS, Ohio (WCMH) – Donald Trump’s support seems to have paid off.

JD Vance, a Cincinnati-area author and venture capitalist who was once polling in the single digits, is projected to win Ohio’s crowded Republican U.S. Senate primary three weeks after being endorsed by the former president.

The Associated Press called the race at 9:34 p.m. Tuesday, just over two hours after polls closed and more than a year after campaigning began to replace retiring Republican U.S. Sen. Rob Portman. Vance was leading with 31% of the vote when the AP projected his victory, followed by top challengers Josh Mandel (25%) and Matt Dolan (22%)

Ohio’s GOP Senate contest was one of the most-watches primaries nationwide, as experts see it crucial to the future party makeup of the nation’s highest legislative body, currently split 50-50 with Vice President Kamala Harris the tiebreaker.

Candidates infused tens of millions of dollars of personal money into their campaigns, which spent tens of millions more on TV ads, a rarity for a midterm primary. But Vance emerged victorious with Trump’s endorsement, something that every candidate but Dolan sought.

Watch: JD Vance on GOP Senate results

Vance, 37, will face Youngstown-area U.S. Rep. Tim Ryan, 48, in November after Ryan easily shook off a progressive challenge from former Obama consumer protection official Morgan Harper and a longshot bid from Columbus activist Traci Johnson.

The AP projected Ryan as the Democratic winner 26 minutes after polls closed. Results as of 9:30 p.m. show Ryan with 71% of the vote, followed by Harper (17%) and Johnson (12%).

Watch: Tim Ryan projected winner for Democratic nomination

Vance rose to fame in 2016 after publishing his memoir, “Hillbilly Elegy,” which chronicles an upbringing surrounded by poverty and drug addiction in Middletown, a midsized Rust Belt city north of Cincinnati.

Once a Trump critic, Vance warmed up to the president’s policies while in office. Issues Vance favored in his campaign include upping domestic manufacturing, breaking up large technology companies and prioritizing the U.S.-Mexico border over help for Ukraine.

Ryan’s TV ads have focused on issues that can more easily cross party lines, like trade, supporting police and economic threats from China. His campaign website also notes support for more traditional liberal causes like abortion rights, environmental protection and fighting institutional racism.