WASHINGTON (Reuters) - Democratic Senator Sherrod Brown of Ohio said on Thursday he would not enter the 2020 U.S. presidential race, but would work to help the party recapture the White House and battle Republican President Donald Trump’s “phony populism.”

FILE PHOTO: Senator Sherrod Brown (D-OH) questions Jerome Powell on his nomination to become chairman of the U.S. Federal Reserve during a hearing before the Senate Banking, Housing and Urban Affairs Committee in Washington, U.S., November 28, 2017. REUTERS/Joshua Roberts/File Photo

Brown, who just wrapped up an exploratory month-long tour of four early voting states, said he was confident the growing field of Democratic White House contenders would carry on his fight for workers.

“We’ve seen candidates begin taking up the dignity of work fight, and we have seen voters across the country demanding it,” Brown said in a statement. “It is how we beat Trump, and it is how we should govern.”

Talking to reporters outside the Senate chamber, he said he did not have a lifelong ambition to be president and the tour had been designed to elevate his pro-worker message within the party.

“In that sense, it was mission accomplished,” Brown said. “I look forward to going back to the Senate where I think I can be most effective.”

Brown, a liberal with strong ties to the labor movement, had not registered significant support in most opinion polls of a Democratic field that includes better-known fellow senators such as Kamala Harris of California, Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts.

His decision is certain to increase speculation that former Vice President Joe Biden, another Democrat with a history of appealing to working-class voters, is likely to enter the race. Former Congressman Beto O’Rourke of Texas is also expected to announce a decision soon.

Three other possible Democratic contenders - former New York Mayor Michael Bloomberg, former U.S. Attorney General Eric Holder, and U.S. Senator Jeff Merkley of Oregon - also announced this week that they would not run.

Brown had easily won re-election to the Senate in November in Ohio, even though Republicans captured every other statewide office. That feat impressed many Democrats looking to take back the industrial states Trump swept on his way to victory in 2016, and sparked talk about a Brown candidacy.

On his exploratory tour, Brown argued he could be a unifying force in a party debating whether to focus on winning back working-class voters or rallying the suburban, women and minority voters who fueled the party’s gains in November’s congressional elections.

“It’s not an either/or,” Brown said when he kicked off the tour in late January. “We can do both.”