Vivek Ramaswamy, the 38-year-old entrepreneur and political newcomer who briefly made a splash with brash policy proposals and an outsize sense of confidence, dropped out of the race for the Republican White House nomination after a disappointing fourth-place finish in the Iowa caucuses.
He then immediately endorsed former President Donald J. Trump for the White House.
“We did not achieve the surprise that we wanted to deliver tonight,” he said in Des Moines on Monday night.
Mr. Ramaswamy, who funded much of his campaign from a personal fortune made in biotechnology and finance, was an unlikely contender at one point. He clung closely to Mr. Trump, vowing to support him even if he was convicted of felonies, promising to pardon him if elected to the White House, and saying he would voluntarily remove his name from the ballot in states that succeeded in knocking Mr. Trump from the ballot as an “insurrectionist” disqualified by the Constitution.
Then two days before the Iowa caucuses, Mr. Trump’s campaign turned on him, declaring him a fraud, and the former president — after months of warmth toward his would-be rival — demanded that voters reject Mr. Ramaswamy and vote for him.
By then, the Harvard-educated Mr. Ramaswamy had embraced increasingly apocalyptic conspiracy theories; spoke of a “system” that would block Mr. Trump from office and install a “puppet,” Nikki Haley; called the Jan. 6, 2021, attack on the Capitol an “inside job” orchestrated by federal law enforcement; and begun trafficking in the racist theory of “replacement” that holds falsely that Democrats are importing immigrants of color to supplant white people.
The theory, which has fueled white supremacist rampages in Buffalo, N.Y., Pittsburgh and El Paso, Texas, “is not some grand right-wing conspiracy theory,” he said in one Republican primary debate, “but a basic statement of the Democratic Party’s platform.”
Mr. Ramaswamy’s opening gambit was to say that, with his superior grasp of the Constitution and civil service laws, he would take Mr. Trump’s America First agenda further than the former president ever could.
That would mean immediately eliminating the Department of Education, F.B.I. and Internal Revenue Service by executive order, cutting the federal work force by 75 percent in a mass layoff, without Congress’s approval, and pulling back America’s foreign military commitments, first in Ukraine but also eventually in Israel and Taiwan.
His isolationist foreign policy gave rivals a ripe target to attack him on, but his bleak vision of millennial and Generation Z voters “starved for purpose, meaning and identity,” with a black hole in their hearts had surprising resonance with older voters.
He used the debate stage to clash fiercely with Republican rivals for the nomination not named Trump, mocking Gov. Ron DeSantis of Florida for what he said were high heels on his boots, calling Ms. Haley, the former South Carolina governor, a stooge for China and the defense industry, and tarring the entire field as pawns of the wealthy financiers of their super PACs. He even called the G.O.P. a “party of losers.”
Such tactics initially gave surprising traction to a businessman who had never held elective office and was known only to a narrow slice of the electorate familiar with his books decrying “Woke Capitalism” and investment strategies aimed at environmental progress and social consciousness. He made a splash at the Iowa State Fair rapping to a recording of his idol, Eminem.
His support among Republican primary voters in a composite of national polling spiked the day of the first Republican debate at 11.6 percent, putting him in third place, just behind Mr. DeSantis and well ahead of the rest of the field.
But he slipped back to the pack as his efforts to gain attention and a penchant for stretching the truth yielded caustic responses from his rivals and appeared to grate on the voters. The second Republican primary debate, in September, featured Ms. Haley telling Mr. Ramaswamy, “every time I hear you, I feel a little bit dumber.”
During the third debate in November, Ms. Haley called Mr. Ramaswamy “just scum” after he accused her of hypocrisy on China because her daughter used the Chinese social media platform TikTok.
By then, Ms. Haley had overtaken Mr. Ramaswamy for third place in national polling. His dogged campaigning in New Hampshire, which in late summer had him vaulting to second place, lost its magic. He blitzed Iowa with by far the most events — rallies, round tables, podcasts and interviews seemingly with anyone with a microphone — but could not regain altitude.
Mr. Ramaswamy had privately told backers that his strategy was to cling to Mr. Trump in the hope that the former president’s myriad legal battles would force him out of the race — and Mr. Ramaswamy would be the logical next choice for Mr. Trump’s most ardent supporters. By the end of September, he had contributed nearly $17 million of his own money.
But with Mr. Trump making it clear not even a conviction would force him from the race, Mr. Ramaswamy’s strategy and self-funding proved unsustainable.