WASHINGTON — Cory Booker has ended his presidential campaign.

“It’s with a full heart that I share this news -- I’ve made the decision to suspend my campaign for president,” Booker said Monday in an email to supporters. "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.

Stuck in single digits in polls and trailing most of his Democratic rivals in fundraising, the New Jersey senator said he couldn’t compete.

“Our campaign has reached the point where we need more money to scale up and continue building a campaign that can win — 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,” Booker said in an email to supporters.

He had bet all his chips on doing well in the Feb. 3 Iowa caucuses, including launching a $500,000 advertising campaign, but failed to move in the polls and did not qualify for Tuesday’s debate in Des Moines. The impeachment trial against President Donald Trump would find him in Washington rather than appealing to Iowa voters.

Booker, though, had planned to return to Iowa on Tuesday, though not for the debate, and again next weekend. He also had four fundraisers scheduled during the week.

He was the latest minority candidate to leave what had been the most diverse field of presidential hopefuls in history. All six candidates in Tuesday’s debate, for example, will be white.

New Jersey Democrats, who had quickly lined up behind Booker when he entered the presidential race, lamented his departure.

“Cory ran a campaign based on a bold vision and an even bolder optimism,” Gov. Phil Murphy said on Twitter. “He changed the presidential race by promising to bring our nation together instead of sowing division. I know he will continue fighting every day for justice and fairness for all.”

U.S. Sen. Robert Menendez, D-N.J., said, “Cory’s unwavering message of fairness, faith and coming together in common purpose is exactly the path our nation needs to heal and move forward.”

“Cory’s ideas and ideals have undoubtedly left a mark on this race, becoming our national voice on criminal justice reform and putting forth the most sweeping and aggressive plan to attack the epidemic of gun violence destroying lives and communities."

And state Senate President Stephen Sweeney, D-Gloucester, said: “His message of inclusion and compassion was a much needed, positive force in the most important presidential race of my lifetime. His voice helped shape the conversation around race and unity throughout the campaign and across the country.”

Several past and current 2020 presidential candidates also praised Booker.

Cory, you campaigned with joy and heart, and instead of just talking about bringing people together, you did it every day. You made our politics better just by running. Grateful to you and looking forward to your continued leadership. — Joe Biden (@JoeBiden) January 13, 2020

.@CoryBooker—every moment on the campaign trail with you, my dear friend, was a joy. I'm incredibly proud of the issues you elevated and the work your team put in day in and day out to fight for justice. We’re all better because you were in this race. — Kamala Harris (@KamalaHarris) January 13, 2020

Thank you, @CoryBooker. You've always been a powerful voice for justice and equality, and you've made this primary stronger. I know you will continue to be a leader in the fight to defeat Donald Trump and build a stronger future for America. pic.twitter.com/5rAwSS2wPR — Elizabeth Warren (@ewarren) January 13, 2020

Trump took one last shot at Booker, who he had attacked several times at rallies during the 2018 midterm elections.

Really Big Breaking News (Kidding): 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! — Donald J. Trump (@realDonaldTrump) January 13, 2020

Booker was considered a top tier candidate when he entered the race in February 2019. But he hovered in the low single digits in opinion polls, even as he built strong organizations to get out the vote in the early primary and caucus states.

His soaring rhetoric inspired audiences and won him kudos at every debate he participated in, but failed to translate into support. He failed to meet the thresholds for both the December and January debates.

His paths to victory were blocked by other candidates. African American voters shunned both Booker and Kamala Harris (before she dropped out) in favor of former Vice President Joe Biden, who served under the first black president, Barack Obama.

While Booker had run New Jersey’s largest city, Newark, another mayor, Pete Buttigieg, of South Bend, Indiana, captured far more attention.

His calls for unity and to heal America’s political divisions fell on the deaf ears of Democratic voters infuriated by the policies and the rhetoric of Trump and wanting someone as angry as they are.

Even at the end, Booker made no apologizes for the type of campaign he ran.

“I’m proud of the ideas we brought to this Democratic primary and, more importantly, the values we championed throughout — that the only way we make progress is by bringing people together — even when we were told that our approach couldn’t win. Because our values must always be our values, even when that’s not convenient,” Booker said.

Despite long-standing ties to Wall Street and Silicon Valley, he raised far less campaign cash than many of his opponents. He also had to face self-funding billionaires Tom Steyer and Michael Bloomberg.

And while candidates like Bernie Sanders and Elizabeth Warren relied on well-developed networks of small-dollar donors, Booker hadn’t raised money for a race since 2014 and therefore trailed in assembling such a list of people willing to give over and over again.

At one point, Booker even talked about prematurely ending his campaign unless he raised $1.7 million during the last 10 days of September. He surpassed that goal.

He instead will run for re-election to the U.S. Senate.

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.

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