WASHINGTON

U.S. Sen. Cory Booker became the latest Democrat to end a 2020 White House run Monday, leaving the increasingly narrow field as primary season rapidly approaches. 

Booker thanked his supporters in a video message, telling them he now looks forward to hitting the campaign trail for whomever the party picks to challenge U.S. President Donald Trump in November's contest.

"But for now I want to say thank you," he said. "Campaigning over this past year has been one of the most meaningful experiences of my life; meeting you, meeting people across this country who believe, who know, that we might have challenges right now in our nation, but together we will rise."

Booker had struggled in recent months to rise above low single-digits in national polling, and his fundraising efforts similarly failed to gain traction as a series of similarly-polling candidates suspended their campaigns ahead of beginning of the nominating process.

The primary season will begin Feb. 3 with the Iowa caucus, and will quickly ramp up from there with primaries or caucuses being held every week, including on March 3 when over a dozen states will hold contests on Super Tuesday.

Trump reacted glibly to Booker's decision, sarcastically calling it "Really Big Breaking News (Kidding)."

"Now I can rest easy tonight. I was sooo concerned that I would someday have to go head to head with him!" he said on Twitter.

Former U.S. President Joe Biden continues to lead the diminishing pack of 2020 Democrats with Sen. Bernie Sanders trailing roughly nine points behind in national polling followed by Sen. Elizabeth Warren.