Former Texas Rep. Martin Frost dropped out of the race for Democratic national chairman on Tuesday after failing to win the backing of organized labor, winnowing the field to front-runner Howard Dean (search) and three challengers.

Frost's decision came hours after AFL-CIO (search) leaders decided not to make an endorsement in the race for Democratic National Committee (search) chairman.

Frost had counted heavily on organized labor to give him a boost against Dean. Many in the AFL-CIO were prepared to back Frost at one point, but he had not shown enough movement in the race to win labor support, union officials said.

The former congressman said Tuesday he had called Dean, the former presidential candidate, and "congratulated him for running a strong campaign. The challenge ahead for Governor Dean will be to unite the party, rebuild the DNC and win elections in every region of the country."

Frost aides said the Texan did not endorse a candidate in the race. Earlier in the day, David Leland, former chairman of the Ohio Democratic Party, dropped out and endorsed Dean.

"I want to thank Congressman Martin Frost and Chairman David Leland for lending their ideas and vision to this race," Dean said. "While I am encouraged by the news of the day, this race is still not over."

Democratic activist Donnie Fowler's campaign was fighting on, along with activist Simon Rosenberg and former Indiana Rep. Tim Roemer.

"The AFL-CIO denied Dean their endorsement today," said Kirsten Powers, a Fowler spokeswoman. "This race has only two candidates who have produced any votes among DNC members so far — Fowler and Dean. At this point only one-third of DNC members have expressed their commitment to a candidate."

Roemer spokesman Ruben Pulido said the former Sept. 11 commissioner is staying in the race because Democrats need an effective spokesman on national security issues who will welcome more voters into the party.

Rosenberg spokesman Guillermo Meneses said: "We're talking to our friends and supporters. Simon is listening to their guidance and advice. At this point, we're moving forward"

At the AFL-CIO political committee meeting Tuesday, "some were for Dean, some for Frost but they didn't want to get into a contest. We thought the best position for the American labor movement, let the delegates and individual unions decide for themselves," said Gerald McEntee, president of the American Federation of State, County and Municipal Employees and chair of the AFL-CIO political committee.

"At this juncture, I believe it's a fait accompli," McEntee said of Dean's bid for chairman.

The AFL-CIO decision came a day after state party leaders endorsed Dean. Former Denver Mayor Wellington Webb dropped out of the race and endorsed Dean on Monday.