Washington ? It’s home to Big Bird, Arthur, Bill Moyers and Jim Lehrer – and not normally a source of great controversy. But these days, PBS finds itself at the center of a political uproar over whether public television promotes a liberal agenda.

The man alleging the bias is Kenneth Y. Tomlinson, a Republican who heads the Corporation for Public Broadcasting. CPB provides federal funding to public broadcasters including the Public Broadcasting Service, which receives about 15 percent of its operating budget, or $48.5 million, from the corporation.

PBS has denied the charges of a liberal slant. But following the criticism, it moved this month to hire an ombudsman to review its programs and announced a revision of its editorial practices. Among them: a requirement that commentary and opinion be labeled as such.

Democratic lawmakers worry that Tomlinson is angling to turn public TV into a spokesman for the GOP – contrary to the mission of the corporation, which Congress set up in 1967 to shield public broadcasting from political influence.

As CPB chairman, Tomlinson has failed miserably, says Sen. Byron Dorgan, D-N.D., a longtime supporter of public broadcasting.

“What Mr. Tomlinson has been doing is very destructive to the interests of public broadcasting,” Dorgan said. “The Corporation for Public Broadcasting would be better off with a fresh start with somebody who is not spending their time claiming that the public broadcasting system is unfair.”

Adding to the Democrats’ unease: the new president of the corporation, Patricia S. Harrison. She was co-chairwoman of the Republican National Committee from 1997 to 2001.

Harrison was named to the post Thursday, the same day that the House voted to rescind proposed cuts of $100 million to the corporation’s budget for next year. Public broadcasting supporters had mounted a furious lobbying campaign against the cuts, bringing Clifford the Big Red Dog and other PBS characters to a rally on Capitol Hill.

PBS says the proposed cuts would have severely impacted “Sesame Street,” “Clifford,” “Between the Lions” and other popular children’s shows.

“That federal funding really acts as a spark plug that causes all of this other money to be attracted,” said John F. Wilson, senior vice president of programming at PBS. “Without that, it’s sort of like taking the keystone out of an arch and expecting the arch to stay up.”

Critics scoff at the notion that public broadcasting can’t survive without the federal help.

“These stations are fat and happy. They’re sitting on millions, if not billions of dollars, in property and equipment and very large salaries. These people are not going anywhere,” said Tim Graham, director of media analysis at the Media Research Center, a conservative watchdog group.

Donations could also make up some of the difference, says Graham. He said donations increased the last time public broadcasters found themselves in a big brawl with Congress over funding.