One day after Sen. Lindsey O. Graham (R-S.C.) entered the 2016 GOP presidential race, Richard N. Wilkerson joined the finance team trying to raise funds for a quixotic bid that ended months later as the senator traded insults with Donald Trump.

Less than five years later, Wilkerson began supporting another long shot: Democrat Jaime Harrison, who is trying to knock off Graham in his bid for a fourth Senate term.

“We need people like Jaime who will get us to listen to each other and craft the best decisions for all of us and stop the bitter win/lose that is dividing us,” Wilkerson, the former CEO of Michelin North America, headquartered in Greenville, S.C., wrote in a newspaper op-ed in early June.

So ended Wilkerson’s more than a decade of support for Graham. And Harrison’s campaign is no longer considered a fluke.

In a state that President Trump won by 14 percentage points in 2016, Harrison has touted his personal story of his early years living in a mobile home in rural Orangeburg to attending Yale University and Georgetown Law School as he tries to make history by becoming the first Black Democrat popularly elected to the Senate from the Deep South.

Based on his fundraising surge and consistent tight polling, a prominent independent political analyst moved the race into its “toss-up” category Wednesday.

Strategists in both parties have never viewed South Carolina as a tipping point for the Senate majority, believing that if Harrison could pull off the biggest upset of 2020 it would mean Democrats had already won many seats.

As the race has grown closer, that view might change, particularly as the Democratic candidate in North Carolina, Cal Cunningham, finds himself enmeshed in a sex scandal that could hand that race to Republicans.

Regardless, Harrison’s candidacy is a potential political earthquake. Black Democrats in the Deep South have historically been encouraged to run for the House in politically safe majority-minority districts, while White moderates like Cunningham find the establishment’s financial backing for statewide Senate races.

Harrison and Raphael Warnock, a minister in Atlanta running in a Georgia special election to try to become that state’s first Black senator, are trying to upend that thinking.

Moreover, with Sen. Tim Scott the only Black Republican in the Senate, a Harrison win would make South Carolina, the birthplace of the Civil War, the first state to have concurrently two elected Black senators.

Harrison still has to thread a very difficult needle. In the last seven Senate races in South Carolina, no Democrat has reached 45 percent of the vote and the late Ernest “Fritz” Hollings was the last Democrat to win, in 1998.

Harrison is trying to forge a new coalition, rooted in a historically high Black turnout but also appealing to disgruntled Republicans such as Wilkerson and the independent-minded voters in Charleston’s suburbs who two years ago backed Rep. Joe Cunningham (D).

Harrison, 44, is a veteran Washington insider — he once worked for House Majority Whip James E. Clyburn (D-S.C.) and spent eight years as a lobbyist — but he has turned the race into a referendum on Graham’s nearly 26 years in Congress.

He highlights Graham’s constant political evolution: Originally a hard-charging conservative, he turned into a moderate dealmaker who vehemently opposed Trump in 2016, only to reverse course and become a close presidential ally.

In their debate Saturday, Harrison took shots at Graham, now the Judiciary Committee chairman overseeing next week’s Supreme Court confirmation hearings, for another reversal after recent promises that he would not consider a nominee this close to an election.

“My grandfather always taught me, he said, ‘Jaime, a man is only as good as his word,’ ” Harrison said. “Well, senator, how good is your word when you made a promise to the American people?”

Graham initially dismissed the close nature of his race, telling reporters in the Capitol on Sept. 16 that a Quinnipiac poll showing a tied race was “very flawed” and claiming it undercounted Republicans.

“We’re taking it seriously,” he said.

Then a CBS News poll showed the incumbent leading by one percentage point, and another Quinnipiac poll showed the race tied.

By the debate in Columbia, Graham turned on Harrison and tried to declare that he would link forces with liberal Democrats in a “nightmare scenario,” giving them the presidency and total control of Congress.

“Capitalism vs. socialism. Conservative judges vs. liberal judges. Law and order vs. chaos,” the Republican said, fully realizing how close the race had become.

Graham, 65, has never run in a competitive general-election race, winning all three terms in the House and three more in the Senate by double-digit margins.

That inexperience is showing.

Graham has looked weak pleading for donations during Fox News appearances and spent many weekends this summer in Washington playing golf with Trump, rather than campaigning back home.

Graham also must spend next week in a Senate hearing room overseeing Judge Amy Coney Barrett’s nomination, while Harrison continues to overwhelm him on the airwaves.

In the last two weeks, Harrison has spent $15.5 million on TV advertising while Graham’s campaign barely cleared $3.5 million, according to Jessica Taylor, the Senate race editor at Cook Political Report.

GOP super PACs reluctantly placed $16 million on the Palmetto State’s TV airwaves to try to defend the seat.

But Harrison and his allies have already booked $68 million worth of advertising, overwhelming the $37 million that Graham and his allies intend to spend.

And Harrison’s fundraising continues to surge, particularly after the death of Supreme Court Justice Ruth Bader Ginsburg last month.

The Democrat’s campaign, a week after the third-quarter fundraising deadline, has taken the unusual stance of not announcing its financial haul, only noting that federal law requires those numbers be released by Oct. 15.

It’s possible that his team simply does not want Graham to know just how much money he raised to keep his outside allies from pumping more money into South Carolina.

Some think Harrison’s quarterly report could approach, or even eclipse, the $38.1 million raised by Beto O’Rourke in the summer of his 2018 race in Texas, believed to be the largest quarterly fundraising haul ever in a Senate race.

And Harrison has done this without half the attention of O’Rourke, whose race against Sen. Ted Cruz (R), reviled by liberals, was the highest-profile race in the nation, even spawning a documentary film.

That O’Rourke lost, narrowly, causes a bit of fear among Democrats, reminding themselves to think with their heads, not their hearts, in such a traditionally conservative state.

Democrats got their hopes too high also in 2016, when Jason Kander, a former Army intelligence officer in Afghanistan, ran what even Republicans conceded was the best Senate campaign in the nation.

However, Kander could not overcome Missouri’s deep conservative tilt, narrowly losing to Sen. Roy Blunt (R).

But Graham knows he is in trouble. Democratic presidential nominee Joe Biden is not as unpopular as Hillary Clinton was four years ago in South Carolina, so Graham tries to link Harrison to far-left liberals in Washington.

He warns that Harrison’s support is fueled by the senator’s newfound allegiance with Trump.

“This election is about taking me out,” Graham said during Saturday’s debate, unintentionally noting that the race has turned into a referendum on his own political behavior, which is never a good thing for an incumbent.

“They hate me. This is not about Mr. Harrison.”