In September 2021, former Senator David Perdue was hemming and hawing about operating for governor of Georgia. Over dinner with an outdated good friend on Sea Island, he pulled out his iPhone and confirmed the record of calls he’d gotten from Donald J. Trump, lobbying him to make the leap.

“He stated Trump known as him on a regular basis,” stated Martha Zoller, a former aide to Mr. Perdue who now hosts a chat radio present in Gainesville, Ga. “He confirmed me on his cellphone these a number of current calls and stated they had been from the president.

Ms. Zoller and a legion of different former Perdue aides and advisers informed the previous senator that operating was a foul thought. He listened to Mr. Trump as an alternative.

Now, Mr. Perdue is staring down an epic defeat by the hands of Gov. Brian Kemp, the Republican whom Mr. Trump has blamed for his 2020 loss greater than every other individual. The Perdue marketing campaign is ending the race low on money, with no advertisements on tv and a candidate described even by his supporters as lackluster and distracted.

“Perdue thought that Trump was a magic wand,” stated Newt Gingrich, the previous Home speaker and a Trump ally, who was amongst Mr. Perdue’s highest-profile Georgia supporters. “Looking back, it’s laborious to grasp David’s marketing campaign, and it’s definitely not the marketing campaign these of us who had been for him anticipated.”

Mr. Perdue’s impending downfall in Tuesday’s major for governor looms as the most important electoral setback for Mr. Trump since his personal defeat within the 2020 election. There may be maybe no contest through which the previous president has completed extra to attempt to affect the result. Mr. Trump recruited, promoted and cleared the sector for his ally, whereas assailing Mr. Kemp, recording tv advertisements and giving $2.64 million to teams serving to Mr. Perdue — by far essentially the most he has ever invested in one other politician.

But the race has uncovered the boundaries of Mr. Trump’s sway, particularly in opposition to entrenched Republican incumbents.

Mr. Perdue’s failures weren’t simply of his personal making. He was outflanked by a savvy incumbent in Mr. Kemp who exploited the powers of his workplace to chop off Mr. Perdue from allies — together with Mr. Perdue’s personal cousin Sonny, a former governor and Trump agriculture secretary whom Mr. Kemp’s allies appointed chancellor of the College System of Georgia.

Mr. Kemp additionally appeared to punish those that crossed him: One congressional seat was drawn to exclude the house of a candidate whose father, a Perdue supporter, had publicly criticized the governor.

And he supplied goodies to voters, together with a gas-tax vacation that conveniently runs by way of the tip of Might, simply previous the first.

On Thursday, as Mr. Perdue campaigned outdoors the Semper Fi Bar and Grille in Woodstock, Ga., he was not conjuring up a path to victory however haggling over the scope of his extensively anticipated defeat, after a Fox Information survey confirmed him down 32 share factors.

“Hell no, I’m not down 30 factors,” insisted Mr. Perdue, whose marketing campaign didn’t reply to requests for remark for this text. “We could not win Tuesday,” he added, “however I guaran-damn-tee-you we aren’t down 30 factors.”

The important thing threshold on Tuesday is 50 p.c: Mr. Kemp should win an outright majority within the five-candidate discipline to keep away from a one-on-one runoff in June.

The story of Mr. Perdue’s effort is much less considered one of political collapse and extra of a failure to launch. From the second he introduced his candidacy in December, Mr. Perdue by no means demonstrated the identical dedication to profitable that he displayed in his first Senate race in 2014.

His case for ousting Mr. Kemp was at all times largely based mostly on assist from the previous president. Mr. Perdue argued at his marketing campaign introduction that the governor had so alienated the celebration’s Trump trustworthy that they’d not rally round Mr. Kemp in opposition to Stacey Abrams, the presumptive Democratic nominee and a number one villain for Republicans.

However Mr. Perdue, 72, a rich former chief government of Greenback Normal, by no means got here near matching the $3.8 million of his personal cash he put into his 2014 Senate race. He invested simply $500,000 in his bid for governor.

That’s lower than he and his spouse spent final yr for a waterfront lot on a secluded peninsula on scenic St. Simons Island, a purchase order made not lengthy after his runoff defeat by the hands of a then-33-year-old Democrat that delivered Senate management to Democrats. A allow to construct an almost 12,000-square-foot mansion value an estimated $5 million — on land together with “over 625 ft of lake frontage,” in line with the itemizing — was granted two weeks after he declared his candidacy, data present.

Mr. Trump has concurrently invested closely in Mr. Perdue, along with his $2.64 million, and sought to keep away from blame because the candidate has faltered, telling The New York Instances in April that the information media’s focus “must be on the endorsements — not the David Perdue one” to measure his affect.

Mr. Trump’s final rally in Georgia got here in late March. He didn’t return, as Perdue allies had hoped, as an alternative holding a convention name for supporters in early Might.

“I’m with David all the way in which as a result of Brian Kemp was the WORST governor within the Nation on Election Integrity!” Mr. Trump insisted Friday on his Fact Social messaging platform.

Mr. Perdue, like candidates for governor in Idaho and Nebraska this month, realized {that a} Trump endorsement alone doesn’t guarantee the assist of Trump voters or Trump donors.

“The Trump endorsement is essential, nevertheless it’s solely an endorsement,” stated former Consultant Jack Kingston, who misplaced the 2014 Senate major to Mr. Perdue and is a former Trump adviser. “It’s not a military of infrastructure and door-knockers the way in which it will be when you’ve got the Sierra Membership or the N.R.A. or the A.F.L.-C.I.O.”

The juxtaposition between the Kemp and Perdue camps was significantly stark on Friday.

Mr. Kemp was outdoors Savannah, saying that Hyundai was investing $5.5 billion in an electrical battery and car manufacturing plant, one of many largest financial growth initiatives in Georgia historical past. There was a champagne toast.

Mr. Perdue was close by holding an endorsement occasion with Sarah Palin, the 2008 Republican vice-presidential nominee, who’s making her personal comeback try in a Home race in Alaska.

“I might moderately be standing on the stage saying 7,500 jobs than standing subsequent to Sarah Palin,” stated Mr. Kemp’s lieutenant governor, Geoff Duncan, a fierce Trump critic who opted to not run for re-election this yr.

Randy Evans, a Perdue supporter who served as ambassador to Luxembourg within the Trump administration, stated the Kemp operation had been ruthless in utilizing what he known as the “bullying” powers of the governorship.

Mr. Evans’s son, Jake, is operating for Congress within the Atlanta suburbs. When Kemp-aligned Republican legislators drew new traces in redistricting, the youthful Mr. Evans was instantly drawn out of the district through which he had been planning to run.

“They minimize a sliver in regards to the measurement of your little finger,” the elder Mr. Evans stated. “Jake needed to transfer, purchase a brand new home.”

Mr. Kemp, 58, leveraged the powers of incumbency in different essential methods. He signed a measure to supply tax refunds of as much as $500 for married {couples}, then introduced on Might 11, after early voting had begun, that these checks had been within the mail. He appealed to rural Georgians by elevating pay for lecturers, and happy conservatives by signing sweeping laws to limit voting entry, increase gun rights and forbid faculty masks mandates.

Mr. Perdue’s efforts may appear feeble as compared. In March, he attacked Mr. Kemp for recruiting an electrical truck maker to open a manufacturing unit in rural Georgia — creating hundreds of jobs — as a result of George Soros, the outstanding Democratic donor, had just lately invested within the firm.

The Kemp-Perdue contest was steeped within the drama of private betrayal.

Mr. Kemp had spent weeks campaigning with Mr. Perdue earlier than the senator’s defeat within the January 2021 Senate runoff election. By then, Mr. Kemp had infuriated Mr. Trump by defending the legitimacy of Georgia’s presidential outcomes.

Final spring, Mr. Kemp’s aides stated, Mr. Perdue assured Mr. Kemp that he didn’t intend to run for governor. That June, Mr. Perdue launched the governor on the Georgia Republican Get together’s annual conference.

However Mr. Kemp, cannily, had already begun the method of putting in Sonny Perdue, a well-liked former governor, to run Georgia’s state universities — an appointment that successfully put him on the sidelines. (Sonny Perdue, by way of a spokesman, declined to remark.)

Mr. Kemp additionally pre-emptively secured the loyalty and fund-raising would possibly of Alec Poitevint, a South Georgia businessman who had served as marketing campaign chairman for David Perdue’s Senate campaigns and Sonny Perdue’s campaigns for governor — considered one of some ways the Kemp operation boxed out Mr. Perdue financially.

Mr. Poitevint stated he was amongst a number of longtime David Perdue supporters who had urged him to not run.

“I didn’t suppose it was critical,” Mr. Poitevint stated. “I expressed the truth that I didn’t agree with it, that I believed that the governor had completed a terrific job and deserved re-election.”

Shunned by the state’s political institution, Mr. Perdue tried framing himself as a political outsider — “I’ve been an outsider since I received into politics,” he stated on Thursday — however that may be a troublesome case to make for a former senator boasting of his assist from a former president.

Even Mr. Trump’s $2.64 million infusion was swamped by the $5.2 million in tv advertisements paid for by the Republican Governors Affiliation to assist Mr. Kemp.

For all of Mr. Trump’s assaults on Mr. Kemp, the governor by no means struck again. Mr. Kemp’s advisers imagine that self-discipline helped present permission for even essentially the most devoted Trump supporters to stay with the governor.

Mr. Perdue’s marketing campaign, in the meantime, was laser-focused on falsehoods about 2020 — repeating Mr. Trump’s lie and blaming Mr. Kemp for President Biden’s election.

Mr. Evans, the previous ambassador who in early 2021 had tried to dealer a peace deal between Mr. Trump and Mr. Kemp, campaigned for Mr. Perdue however stated he noticed little effort to outline a particular platform.

​​ “So far as having an existence that existed impartial of Trump, I actually didn’t see that materialize,” Mr. Evans stated.

Mr. Kemp’s lieutenant governor, Mr. Duncan, summarized the arc of the Perdue candidacy.

“David Perdue made a foul guess six months in the past when he jumped within the race and thought, ‘As a result of Donald Trump likes me, I’m going to win,’” Mr. Duncan stated. “He guess incorrect.”

Maya King contributed reporting. Kirsten Noyes contributed analysis.