Externally, Mr. Scott’s brand of relentless optimism never found traction. Internally, his campaign was plagued by missteps, and a huge sum expected from a key donor never materialized.It was late October and Tim Scott’s campaign manager, Jennifer DeCasper, was trying to rally the troops on an all-staff call, announcing that they would soon relocate to Iowa in a last-ditch move to salvage his floundering presidential bid. She broke the news from the back seat of an Uber, according to four people familiar with the call.As the car bumped through the streets of Chicago after a Scott speech had run long, Ms. DeCasper insisted, “We are not failing.”But by then, even many of those around Mr. Scott believed his candidacy had already run its course.His debate performances were flat. His television ads weren’t working. His operation was burning through far more cash than it was raising. And his super PAC had canceled its own television ads days before Ms. DeCasper’s staff call.There was one other detail that had been closely guarded: The man long expected to be the super PAC’s biggest donor, the billionaire Larry Ellison, wound up not giving anything to the group after Mr. Scott entered the race, according to four people aware of the group’s finances. From 2020 to 2022, Mr. Ellison donated $35 million to Scott-aligned groups, and a huge check had seemed a foregone conclusion when Mr. Ellison showed up at the Scott kickoff and got a shout-out from the stage.Before his run, Mr. Scott telegraphed to allies that he had expected a significant sum to flow into his super PAC, according to three of the people familiar with the discussions and planning, and the super PAC wrote a budget for roughly half the amount that Mr. Scott had predicted. But donations fell well short of even that smaller sum.By early November, Mr. Scott had sunk so low in polls that he barely qualified for the third presidential debate in Miami. Then, on a night last week when he knew he needed a performance that would reinvigorate his flagging candidacy, the biggest splash he made in Miami was the public debut of his girlfriend.Days later, he quit the race on Fox News in an announcement that surprised much of his staff.For a senator from South Carolina who had entered the race with high hopes as the Republican Party’s highest-ranking Black elected official, Mr. Scott, 58, was unable to convert his compelling life story — and more campaign cash at the outset than any other candidate — into concrete support.Externally, Mr. Scott’s brand of relentless optimism never found traction in a contest that has been dominated by the dark and fear-laden campaign of former President Donald J. Trump.“Sometimes the message and the tone don’t align with the moment,” said Rob Godfrey, a veteran South Carolina Republican political strategist who has followed Mr. Scott’s career for years. “It may be that the potential wasn’t realized in this campaign because there is such anger and polarization in the electorate.”Internally, the campaign was plagued by miscommunications, missed opportunities and mistrust. Allies questioned the candidate’s devotion to the race and his decision to lean on a senior team, led by Ms. DeCasper, with so little presidential experience. Mr. Scott himself raised concerns to one person close to him about how the nearly $22 million he brought into the race from his Senate re-election was being spent by others, which further narrowed his circle of trust.“It’s hard for any presidential candidate to surround themselves with people they don’t know and ask them to be loyal to the cause,” Ms. DeCasper, who has worked with Mr. Scott for more than a decade, said in an interview. “I was his longstanding protector and nobody could have done that besides me.”Ms. DeCasper said those who doubted Mr. Scott’s commitment to the cause were misinterpreting his core values.“He made a promise to his mother that he would take her to church every Sunday,” Ms. DeCasper said. It was a promise, she added, Mr. Scott rarely broke. “People without context would see it as a lack of commitment to a presidential campaign,” she said. “But in reality he was committing to being a good senator as well as a good Christian as well as a good son.”In some ways, the debates were the undoing of Mr. Scott. He had entered the first one, in August, primed for a moment as Gov. Ron DeSantis of Florida had faded and he had ticked up in the polls in Iowa. But Mr. Scott was largely absent that evening and never fully recovered. Donors and voters instead gave a fresh look to his fellow South Carolinian, former Gov. Nikki Haley, who had first appointed Mr. Scott to the Senate a decade ago and who supplanted him as Mr. DeSantis’s chief rival for a Trump alternative.Mr. Scott struggled to stand out against Nikki Haley, Ron DeSantis and Vivek Ramaswamy during the primary debates.Todd Heisler/The New York TimesThe fourth debate in December, with its higher polling requirement, had threatened to unceremoniously end the Scott campaign and so, after weekend events in Iowa were canceled because of what his campaign said was a case of the flu, Mr. Scott bowed on Sunday night to the reality that the race was over.His announcement on Fox News on Sunday blindsided most of Mr. Scott’s own aides and supporters, with among the few to know being Ms. DeCasper and Nathan Brand, his communications director.The shock factor was the latest and final sign of a campaign that some criticized as insular at the top. Fund-raising pleas had gone out less than an hour before he had announced his departure. And the suspension of his campaign was not posted on his own account on X, the platform formerly known as Twitter, for nearly three hours.Privately, allies and advisers to Mr. Scott had questioned his dedication to the contest, pointing to a campaign schedule that was less robust than his leading non-Trump rivals. According to a calendar tracked by The Des Moines Register, Vivek Ramaswamy held more than twice as many events as he did in Iowa this year, while Mr. DeSantis had 50 percent more events and even Ms. Haley, who has made Iowa far less central to her candidacy, nearly matched Mr. Scott’s total. (Unlike Ms. Haley and Mr. Ramaswamy, Mr. Scott has a full-time job as a senator.)Questions about Mr. Scott’s future had accelerated after his super PAC pulled its advertising plug, after running about $12 million of the $40 million in ads it had announced reserving over the summer. “We aren’t going to waste our money when the electorate isn’t focused or ready for a Trump alternative,” Rob Collins, the super PAC’s co-chairman, wrote in a blunt memo to donors.Katon Dawson, a former South Carolina Republican Party chairman who is supporting Ms. Haley, called the memo unhelpful. “That was the first thing that sucked the oxygen out,” Mr. Dawson said.But Mr. Scott himself soon echoed that message on CNBC, a relatively rare interview beyond the friendly confines of Fox News.“One of the things that we’ve realized throughout the last several days is breaking through in any of the media with any campaign material is just useless,” Mr. Scott said. “Why waste those resources when you can save them for the end of the campaign when you will have the opportunity to break through.”That opportunity never came.Despite a Black Republican surging to the top of the polls in each of the last two open Republican primaries (Ben Carson in 2016, and Herman Cain in 2012), Mr. Scott never had a breakout moment in 2023, even as polls show he remained well liked by voters.In the end, the party instead seemed satisfied to have Mr. Scott stay in the Senate. The lack of money from Mr. Ellison was symptomatic of a broader trend of donor reluctance.In the first half of 2021, when Mr. Scott delivered the Republican rebuttal to President Biden’s first address to a joint session of Congress, Mr. Scott had nearly 247,000 online donations. This year, when running for president, he had far fewer: under 109,000 online contributions, according to federal records data for WinRed, the company that processes nearly all online Republican campaign contributions.Though Mr. Scott has repeatedly downplayed any interest in the vice presidency, his lack of frontal criticisms of Mr. Trump — and Mr. Trump’s lack of attacks on him — has fueled repeated questions about them as potential running mates.But Mr. Scott, who has previously indicated that he will not seek another U.S. Senate term in 2028, did not foreclose a different political future on Sunday, saying he was listening to the voters in his interview with Trey Gowdy.“They’re telling me, ‘Not now, Tim,’” he said. “I don’t think they’re saying, Trey, ‘No,’ but I do think they’re saying, ‘Not now.’” More