Roffle Mayes Miller Jr., a general contractor and political novice, yesterday became the third candidate to enter the race for the Republican nomination for D.C. delegate.

In a speech to about two dozen supporters gathered at Freedom Plaza in front of the District Building, Miller pledged to challenge the city's "Democratic establishment," which he said has proved incapable of governing well.

"What we have in the District is a machine," Miller said. "The Democrats haven't been able to solve the problems."

Two other Republicans are vying for the nomination in September: political consultant Jim Champagne and former Education Department civil rights chief Harry M. Singleton. The D.C. Republican State Committee has endorsed Singleton for the nomination, but Miller said he thought it was "unfair that they didn't let others come forward."

Miller, 37, has had no experience in local politics. He moved here from Maine, where he said he was active in the Republican Party.

In his speech, Miller touted his experience in business and his willingness to speak out on the issues as evidence of his fitness for office.

Miller said his platform would include gaining access for the District to the White House. "Nobody has access to the current administration," he said. "We need to have a different perspective in the District."