Republican voters’ choice for Virginia governor, a deep-pocketed first-time candidate who plans to run as a business-friendly political outsider, will offer a major test in the post-Trump era of the party’s ability to win back suburban voters who have fled over the past four years.

Glenn Youngkin, who won the Republican nomination on Monday night, had walked a line between his party’s Trump-centric base and appeals to business interests in a crowded field, defeating two rivals who more aggressively courted supporters of former President Donald Trump.

After years of Democratic advances in the state thanks to suburban voters who adamantly rejected anyone linked to the Trump G.O.P., Mr. Youngkin, 54, a former private equity executive, has warned “we can kiss our business environment away” if Democrats retain power in Richmond.

During the nominating fight, he criticized the current governor, Ralph Northam, and his predecessor, Terry McAuliffe, for creating business conditions that cause college-educated residents (read: suburbanites) to move away.

But even as Mr. Youngkin tries to focus on kitchen-table issues, Democrats signaled on Tuesday they would aggressively seek to fuse the nominee to Mr. Trump, by reminding voters of hard-line positions he took in fending off six Republican rivals — including on voting rights, Medicaid expansion and culture-war topics like critical race theory.

Mr. McAuliffe, the polling leader for the Democratic nomination, said in a statement on Tuesday that Mr. Youngkin “spent his campaign fawning all over Donald Trump,” adding that he would “make it harder to vote” and be “a rubber stamp for the NRA’s dangerous agenda.”

Mr. Trump stayed out of the G.O.P. race while the field jockeyed for position, with Mr. Youngkin ultimately emerging as the winner after roughly 30,000 voters cast ranked-choice ballots at 39 locations around the state on Saturday. But the former president jumped in on Tuesday with an endorsement of Mr. Youngkin, although it was primarily an attack on Mr. McAuliffe, a former fund-raiser for Bill and Hillary Clinton, who as a private citizen was in business with Chinese investors.

“Virginia doesn’t need the Clintons or the Communist Chinese running the state,” Mr. Trump said, “so say no to Terry McAuliffe, and yes to Patriot Glenn Youngkin!”

But Mr. Youngkin might consider such effusions unwelcome in a state Mr. Trump lost by 10 percentage points in November.

Mr. Youngkin, 54, was raised in Virginia Beach and has lived in Northern Virginia for 25 years. He defeated two rivals who appealed more directly to the Trump-centric base: Pete Snyder, a technology entrepreneur, and State Senator Amanda Chase, a hard-right supporter of the former president who was censured in a bipartisan vote of the state’s General Assembly for referring to the rioters at the Capitol on Jan. 6 as “patriots.”

Mr. Youngkin’s appeal to Republicans was at least twofold: He is a political blank slate, with no record in elected office for Democrats to attack. And his private wealth — reportedly more than $200 million after he retired as co-chief executive of the Carlyle Group — will allow him to compete financially against Mr. McAuliffe, a prolific fund-raiser.

Mr. McAuliffe raised $36 million for his 2013 election campaign and more than $9.9 million during the past two years, according to the Virginia Public Access Project. Mr. Youngkin has already spent $5.5 million of his own money since entering the race in late January.

Republicans have not won a statewide election since 2009, and Democratic dominance of the once-purple state accelerated under Mr. Trump, with Democrats taking control of both houses of the General Assembly in 2020 for the first time in a generation.

They used their dominance of state government to pass sweeping progressive priorities like more restrictive gun laws and a ban on capital punishment.

But the trend is not irreversible, as some election analysts see it. In the pre-Trump era, Mr. McAuliffe won his first governor’s race in 2013 by just 2.5 percentage points against a hard-right conservative, Kenneth T. Cuccinelli II. Rural regions of southern and southwest Virginia have grown redder even as the populous northern and central suburbs are bluer. There is a theoretical path to statewide Republican victory for a candidate who rouses rural Trump voters, appeals to suburban independents and benefits from lower overall Democratic turnout without Mr. Trump as a motivator.

And Mr. Youngkin has signaled that he would run against the very legislation Democrats have passed, accusing his opponents of pushing Virginia far to the left of most voters’ preferences.

Mr. McAuliffe may be the clear polling leader for the Democrats, but he is conspicuous as the lone white candidate in a field with three Black contenders, in a party whose base is heavily African-American.

In four years in office, Mr. McAuliffe governed as a pro-business Democrat, and he began his campaign for a second term in December on a pro-education note, pledging to raise teacher pay and offer universal pre-K. (Virginia governors cannot serve two consecutive terms.)

Though Mr. Youngkin is not as unrelenting a supporter of Mr. Trump as some of his Republican opponents, he declined the chance at a recent candidates’ forum to distance himself from Mr. Trump’s lies about a rigged 2020 election. Asked about “voter integrity,” he launched into a five-point plan to “restore our trust in our election process.”

During the nominating race, he also pledged to restore a state voter identification law and to replace the entire state board of education. He also said he would create the “1776 Project,” an apparent reference to a curriculum of patriotic education proposed by a commission established under Mr. Trump that has been derided by mainstream historians.

Last month, Mr. Youngkin said it was “a sad thing” that Virginia had expanded Medicaid under the Affordable Care Act, though he acknowledged the clock couldn’t be turned back.

As Mr. Youngkin likely spends generously on TV ads to forge a more soft-focus identity as a pro-business outsider, Democrats are sure to try to keep his earlier positions in front of voters.

“Make no state mistake about it, we are going to point out every step of the way the right-wing extremism of Glenn Youngkin,” Susan Swecker, chair of the Virginia Democrats, said on Tuesday.