New Jersey Senator Cory Booker is out of the race for the Democratic presidential nomination for 2020.

"Friend, it’s with a full heart that I share this news—I’ve made the decision to suspend my campaign for president," he said in an email message to his supporters Monday morning.

Booker continued, "Nearly one year ago, 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 said in the email. "I’ve always believed that. 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. And maybe I’m stubborn, but I’ll never abandon my faith in what we can accomplish when we join together. I will carry this fight forward -- I just won’t be doing it as a candidate for president this year."

He had been languishing in the polls and did not meet the polling threshold for the December debate in Los Angeles. His campaign raised $6.6 million over the final months of the year, far less than the candidates who had made the stage, the Washington Post reported.

The remaining candidates are Michael Bennet, Joe Biden, Michael Bloomberg, Pete Buttegieg, John Delaney, Tulsi Gabbard, Amy Klobuchar, Deval Patrick, Bernie Sanders, Tom Steyer, Elizabeth Warren, and Andrew Yang.

Booker's perceived vulnerabilities left him open to criticism from the progressive wing of the party, who pointed to his moderate record and ties to Wall Street as red flags. During his tenure as mayor of Newark, he famously called Obama's attacks on private equity "nauseating."

He was criticized for rejecting a proposal aimed at lowering prescription drug prices, earning him accusations of "doing the industry’s bidding." He also has an extensive track record of supporting charter schools—putting him closer to Secretary of Education Betsy DeVos than most Democrats on the issue.

Booker is facing re-election for his Senate seat this year and plans to run, according to his former press secretary Tom Pietrykoski.

The Iowa Democratic caucuses are T-21 days away.