Cory Booker ended his presidential campaign Monday and will seek reelection to the U.S. Senate from New Jersey instead, after his message of healing and uplift failed to catch fire in the Democratic primary campaign.

The announcement, just weeks before Iowa holds the first formal contest in the party’s nominating battle, comes after Booker struggled for months to break through in polls or keep pace with the top candidates’ fund-raising.

His lofty calls for love and togetherness frequently won cheers and warm feelings from voters who saw him, but didn’t resonate enough in a time of upheaval and political strife. While many said they liked what they heard, Booker never established a firm base of support or set himself apart in the crowded field — a rare struggle for a senator who has long been a political celebrity.

“It was a difficult decision to make, but I got in this race to win, and I’ve always said I wouldn’t continue if there was no longer a path to victory,” Booker wrote in a post on Medium and a text message to supporters. “Our campaign has reached the point where we need more money to scale up ... money we don’t have, and money that is harder to raise because I won’t be on the next debate stage and because the urgent business of impeachment will rightly be keeping me in Washington. So I’ve chosen to suspend my campaign now, take care of my wonderful staff, and give you time to consider the other strong choices in the field.”

Booker’s departure leaves what was once a historically diverse Democratic field with just three nonwhite candidates, all on the fringes of the race: businessman Andrew Yang, former Massachusetts Gov. Deval Patrick, and Rep. Tulsi Gabbard of Hawaii.

Booker was stuck in the low single digits in polling and failed to qualify for two consecutive Democratic debates, one in December and another set for Tuesday night. He hasn’t been able to pull in significant support from the black voters his campaign strategy relied on.

He was also one of several Democratic senators contending for the nomination likely to be pulled off the campaign trail for the impeachment trial of President Donald Trump, expected to begin soon.

Booker was a finalist to be Hillary Clinton’s vice-presidential pick in 2016. Speculation among political analysts immediately began about whether Booker could be considered again for that role when this year’s Democratic nominee emerges.

As the party battles over whether to challenge Trump with a trusted moderate like Joe Biden or a rousing liberal such as Bernie Sanders or Elizabeth Warren, Booker argued he could re-create the coalition that propelled Barack Obama into the White House. He had admirers in the party’s business and donor class, including on Wall Street and in Silicon Valley, and argued that he could inspire black voters, critical to his party. Booker frequently emphasized his work as mayor of the largely minority and low-income city of Newark, N.J.

His uplifting appeal, built around his personal story as someone whose parents overcame housing discrimination with the help of a white lawyer inspired by the civil rights movement, consistently won cheers at major Democratic events, and many voters said they liked Booker. He frequently spoke of developing “a more courageous empathy” in the country and restoring “civic grace.”

But few seemed to see his message as right for the moment, or Booker as a figure singularly qualified to beat Trump. His numbers never budged despite several well-received debate performances.

One pollster from New Jersey, Monmouth University’s Patrick Murray, frequently described Booker as stuck “in the friend zone.”

Booker has long been seen as a potential presidential contender, covered for years in the national media and frequently featured not just on news programs, but also sitcoms and late-night comedy shows. His first run for mayor of Newark was turned into a heralded documentary, Street Fight, and he recently began dating the actress Rosario Dawson.

Yet in this race, for one of the first times in his political career, Booker struggled to stand out. His major policy ideas, including a “baby bonds” program to create government-funded savings accounts for all newborns, failed to excite Democrats in the same way as proposals from rivals such as Sanders and Warren.

He wasn’t the only black senator in the race until Sen. Kamala Harris of California dropped out. And Pete Buttigieg emerged as another mayor with sterling speaking skills and a gleaming resumé.

Booker stood behind his unifying themes in his message Monday morning.

“I got in the race for president because I believed to my core that the answer to the common pain Americans are feeling right now, the answer to Donald Trump’s hatred and division, is to reignite our spirit of common purpose to take on our biggest challenges and build a more just and fair country for everyone,” he wrote.

“I’ve always believed that,” he added. “I still believe that. I’m proud I never compromised my faith in these principles during this campaign to score political points or tear down others.”

Trump tweeted mockingly, “Booker, who was in zero polling territory, just dropped out of the Democrat Presidential Primary Race. Now I can rest easy tonight. I was sooo concerned that I would someday have to go head to head with him!”

Booker had hoped he could perform well enough in the early states to rally in South Carolina, the fourth state in the nominating contest, where roughly 60% of the Democratic primary electorate is black. But African American voters have largely lined up behind Biden, the former vice president.

Booker will now seek a second full term as a senator from a strongly Democratic state where he is unlikely to face significant challenges in the primary or general elections this year.