Abdul Alim Muhammad, launching the sharpest attack of his Democratic primary campaign to unseat Maryland Rep. Steny H. Hoyer, showered Hoyer yesterday with largely unsubstantiated accusations of dirty politics while Hoyer criticized Muhammad for being so apathetic that he didn't register to vote until recently.

In an appearance with Hoyer on "Fox Morning News," Muhammad said his campaign against Hoyer is an attempt "to set a clean glass down beside a dirty glass, and then let the voters of Prince George's County decide which one they want to drink out of."

After the appearance, Muhammad said in an interview that he had no evidence that Hoyer had done anything illegal, but said Hoyer had contributed to a "generally sleazy atmosphere" in Prince George's politics. On television Muhammad questioned whether Hoyer had helped family members obtain government jobs or contracts, but said later he was uncertain whether his facts were "completely accurate."

Hoyer, saying, "I have a record that stands the test of scrutiny," denied that he had done anything improper and confidently predicted he would defeat Muhammad in the Sept. 11 primary.

"I expect to win handily," Hoyer said. "I think {Prince George's voters} are going to determine that Steny Hoyer has served them effectively . . . . I think that's why I've been reelected with overwhelming majorities from across the community."

Hoyer has represented Maryland's 5th District, which includes most of Prince George's County, for nine years, and holds the fourth-highest leadership position among House Democrats. Muhammad, a physician, is making his first run for elective office and is best known as national spokesman for the Nation of Islam and its leader, Louis Farrakhan.

Although Hoyer is considered a heavy favorite, the contest has attracted attention because of changes in Prince George's racial composition. About half the county's population is black. Muhammad is the first black candidate to challenge Hoyer, who is white.

Yesterday's television appearance was only the second head-to-head meeting between the two -- they sparred earlier this week at a candidates forum -- and by far the most high-profile. Hoyer spent most of the 10-minute exchange fending off attacks by Muhammad, taking the offensive only when he questioned Muhammad's background in politics and public life.

Muhammad "hasn't even voted, ever, in Prince George's County," Hoyer said. "He didn't register until May 10. Jesse Jackson came in in 1980 and 1984 talking about bringing hope to America, but Dr. Muhammad didn't care enough about that campaign to even register to vote in a presidential election."

Muhammad, calling himself "the Muhammad Ali of politics," said that next month's primary will be "the political upset of the century . . . . I'm predicting a knockout." He said that Hoyer "is at the end of his political career."

By most conventional political measures, Muhammad trails Hoyer badly. Hoyer has raised more than $400,000; Muhammad said he has raised no more than $35,000. Muhammad has no plans to run a significant advertising campaign or to use expensive political technology such as targeted mailings or telephone banks. His campaign is primarily a grass-roots effort, consisting of appearances at candidates forums and shopping malls.

Several county politicians said yesterday that most of Muhammad's appearances are concentrated in Prince George's black community and that they have seen little evidence of any Muhammad organization among whites. Hoyer has campaigned vigorously among blacks and whites, winning the support of several black elected officials.

Responding to a question on television yesterday, Hoyer said he did not believe race would be a dominant factor in the election. "My view has always been that . . . Americans of all ethnic and national backgrounds want an effective member of Congress," he said. "They want a member who articulates their views. I think I've done that."

Muhammad did not directly address the issue of race, but said, "It's time for a change in Prince George's County." He said that Hoyer has won in the past because "there's never been an effective challenger. That's going to be different this time."