Former Rep. Beto O’Rourke of Texas is dropping out of the presidential race, ending a campaign in which he struggled for months to recapture the energy of his insurgent 2018 Senate candidacy on a national stage full of other big personalities and liberal champions.

O’Rourke made the decision to quit the race in the middle of this week, on the eve of a gathering today of Democratic presidential candidates in Iowa, according to people familiar with his thinking. He is not expected to run for any other office in 2020, despite persistent efforts by party leaders and political donors to coax him into another bid for the Senate.

His campaign has been under extreme financial strain, and O’Rourke’s advisers concluded that proceeding in the race might have meant making deep cuts to his staff in order to pay for advertising and other measures to compete in the early primary and caucus state.

O’Rourke planned to announce his withdrawal from the race in Iowa this evening and follow up with an email message to his supporters. In that message, a draft of which was reviewed by The New York Times, O’Rourke said he was proud of championing issues like guns and climate change but conceded that his campaign lacked “the means to move forward successfully.”

“My service to the country will not be as a candidate or as the nominee,” he said.

By leaving the race, O’Rourke completes the winding path from his early status as a potential front-runner to his drastic decision over the summer to reframe his candidacy as an activist crusader after the mass shooting targeting Latinos in his home city of El Paso, Texas.

Since then, O’Rourke has campaigned doggedly on issues related to guns and race, calling most notably for federal gun-control policies that would require owners of assault-style weapons to surrender them to the government. That’s a far more aggressive stance than most Democratic presidential candidates have endorsed.

That last phase of his campaign has taken O’Rourke far beyond the early-state circuit and included visits with prison inmates in California and an immigrant community in Mississippi. In an August interview after the El Paso massacre, O’Rourke said his focus would be “taking the fight to Donald Trump” and “being with those who have been denigrated and demeaned.”

In recent weeks, he has also criticized other Democrats in newly strident terms, declaring in September that Sen. Chuck Schumer, D-N.Y. and the Senate minority leader, had accomplished “absolutely nothing” on gun control.

O’Rourke entered the 2020 primary in the middle of March with the aura of a celebrity, cheered by rank-and-file Democrats and admired by no less a figure than former President Barack Obama for his near miss challenge to Sen. Ted Cruz in the nation’s largest red state. He effectively unveiled his run for the White House in a cover story for Vanity Fair in which he declared he was “just born to be in it.” He later described the cover, along with his choice of words, as a mistake.

In the earliest days of his campaign, O’Rourke was a fundraising powerhouse, collecting more than $6 million in his first day as a candidate. But his fundraising cratered almost immediately. He raised more in his first 48 hours than in the following 1,000 days and steadily depleted his campaign treasury by spending more than he was taking in.

And despite the near-heroic status he achieved in the eyes of Democratic voters as a daring challenger to a Republican they loathed — Cruz — O’Rourke found it far more difficult to stand out from a crop of presidential candidates that included other young orators, like Mayor Pete Buttigieg of South Bend, Indiana, and determined progressives like Sen. Elizabeth Warren of Massachusetts.

O’Rourke also came under harsh attack in a June debate from Julián Castro, the former housing secretary and a fellow Texan, who blasted O’Rourke from the left on immigration. O’Rourke, who was not an especially strong debater in his Senate campaign, appeared badly caught off guard.

To O’Rourke and his allies, it has been evident for some time that he was confronting a vanishingly slim path forward. At the last Democratic debate, a pair of O’Rourke’s donors flew to Ohio to meet with him about his campaign and the possibility of him quitting the race to run for Senate in Texas against John Cornyn, who is up for reelection. O’Rourke told them he was not running for Senate, according to people familiar with the matter.

A spokesman to O’Rourke reiterated that stance today. “Beto will not be a candidate for U.S. Senate in Texas in 2020,” said Rob Friedlander, an aide to O’Rourke.

It is unclear whether O’Rourke’s exit will have a significant effect on the larger shape of the Democratic primary race. In a New York Times/Siena College poll released today, O’Rourke was supported by just 1% of likely Democratic caucusgoers in Iowa. He had not yet met the thresholds for participating in the upcoming primary debates in November and December.

O’Rourke may find — as other former candidates have done — that the goodwill of his fellow Democrats returns quickly once he is no longer a competitor for the nomination. He is 47 years old, leaving him plenty of time to consider a return to electoral politics. But in a recent interview with Politico, O’Rourke said that if he did not prevail in the 2020 presidential primary he would not become a candidate again.

“I cannot fathom a scenario where I would run for public office again if I’m not the nominee,” O’Rourke said last month.