Democrat Sherrod Brown 2020 presidential election campaign

Bill Clark | CQ-Roll Call Group | Getty Images

Sen. Sherrod Brown, D-Ohio, participates in the press conference on the nomination of Chad Readler, to be U.S. Circuit Judge for the Sixth Circuit, on Tuesday, March 5, 2019.

Democratic Sen. Sherrod Brown, a noted Wall Street critic seen as a supporter of blue collar workers, will not run for president next year, he announced Thursday.

The Ohio lawmaker said he will instead focus on labor issues as he tries to help a Democratic presidential candidate defeat President Donald Trump. Brown, who has recently traveled around the country on a “Dignity of Work” tour, added that he will push 2020 Democratic candidates to focus on boosting workers.

“I will keep calling out Donald Trump and his phony populism. I will keep fighting for all workers across the country,” the senator said in a written statement. “And I will do everything I can to elect a Democratic President and a Democratic Senate in 2020. The best place for me to make that fight is in the United States Senate.”

Brown’s decision takes one potentially viable candidate from the race to challenge Trump next year. The senator, 66, has long catered to some of the blue-collar voters Trump appealed to in 2016. He could have challenged the president in Ohio, a state every presidential election winner has carried since 1964.

Brown has slammed free-trade deals for sapping Americans jobs and criticized U.S. manufacturers for moving operations overseas. He has called for tighter regulation of Wall Street and stronger consumer protections.

The senator is seen as a progressive on numerous economic issues, but more centrist than many Democratic presidential candidates on other policies. For instance, he has not backed “Medicare-for-all” or a Green New Deal, recent liberal policy priorities.

It is unclear exactly how Brown’s absence from the race will affect other primary contenders, both declared and undecided. He could have conceivably sapped support from former Vice President Joe Biden or Sen. Amy Klobuchar, D-Minn., who have occupied a more centrist lane and will try to appeal to Midwestern voters. Brown also could have competed for supporters of Sen. Elizabeth Warren, D-Mass., or Sen. Bernie Sanders, I-Vt., who have drilled into labor issues and keeping big banks in check.

Widely followed elections forecaster Nate Silver of FiveThirtyEight tweeted that Brown’s decision probably most helps candidates vying for support in the Midwest. He pointed to Klobuchar and potentially Biden, South Bend Mayor Pete Buttigieg and former Rep. Beto O’Rourke (who has not decided whether to enter the race).

He also said Brown’s absence could give Sanders less competuition in trying to gather support from organized labor.

Nate Silver Sherrod Brown tweets

Various early 2020 Democratic primary polls have showed Biden, Sanders, Sen. Kamala Harris, D-Calif. and Warren near the front of the pack. Biden has not yet declared whether he will launch a campaign.

Brown’s “Dignity of Work” tour took him to several early primary states such as Iowa and New Hampshire. His ability to challenge Trump in his home state was seen as a key selling point in 2020.

In November, Brown comfortably won his third Senate term, even as Republicans kept control of the governor’s office.

Subscribe to CNBC on YouTube.