Del. Juanita D. Miller thought something was wrong when state Sen. Albert R. Wynn did not show up for the announcement of her candidacy for reelection. Wynn says he had a scheduling conflict that evening, but her fears were confirmed a few days later when Wynn disclosed his slate for the Sept. 11 primary.

She was not on it.

Now, Miller is running for the state Senate, and she and her "Democratic Coalition" slate are going head-to-head against Wynn and his "Democratic Alliance Team" in a bitter, personal contest that has divided Democrats in Prince George's 25th legislative district.

All the legislative candidates are black in this mid-county district whose population has changed dramatically in recent years from majority-white to majority-black. But the district has a different division now between the older and less affluent inner-Beltway communities and the newer neighborhoods of upwardly-mobile families to the north and east.

Some of the candidates say service to the poorer communities of Suitland, Capitol Heights and District Heights has suffered as affluent residents in Kettering, Largo and Mitchellville have flexed their political muscle.

The criticism is aimed primarily at Wynn, 38, of Largo, who replies with a list of projects he says he has helped get for those areas, including renovating Forestville High School and repaving Silver Hill Road.

Miller, meanwhile, has had to contend with criticism that she is not a serious candidate and, in forgoing her delegate's seat for a senatorial challenge, is motivated mainly by her personal animosity toward Wynn, who cited "philosophical differences" in dropping her from his ticket.

The Democratic candidates -- there is no GOP primary contest because candidates David S. Bernstein and Katharine Garnett will automatically advance to the general election and only 3,377 Republicans registered, compared with 28,369 Democrats -- cite growth, recreation, housing and education as concerns of district voters. But after a slow start, the race has turned more on matters of personality and political alliances.

Running for the House of Delegates on a slate with Wynn, a lawyer, are Del. Ulysses Currie, 53, an educator from Capitol Heights; educator Beatrice Tignor, 45, of Mitchellville; and Michael Arrington, 34, of Largo, executive director of the Maryland Minority Contractors Association. County Council member Jo Ann T. Bell is also on the "Democratic Alliance" ticket.

Wynn's slate is backed, too, by County Executive Parris Glendening and by retiring district delegate and House Speaker Pro Tem Dennis C. Donaldson.

Earlier this month, Miller, 43, of Suitland, formed a slate with announced delegate candidates Kevin L. Jefferson, 30, a Rainbow Coalition staff member who also lives in Suitland, and Carolyn Yvette Mills, 28, of Largo, the ombudsman in the county office of aging.

Bennie L. Thayer, a businessman and Rainbow Coalition activist running against Bell for the County Council, is also on the Miller slate.

Further enlivening the race for the three delegate seats are three Democrats unaffiliated with any slate. They are communications consultant Horace J. Hillsman, 51, of Suitland; anti-hunger lobbyist Darold M. Johnson, 33, of Mitchellville; and teacher John J. Williams, 57, of Capitol Heights.

Williams, who narrowly lost a 1978 race for delegate, said political power has shifted within the district. For example, there were 2,199 registered voters in District Heights in 1982, compared with 1,163 today, while registration in the growing Kettering-Largo area has gone from 938 to 3,185. "We have a new population, and people have not gotten to know each other," he said.

"Very few seem to be addressing the real needs of this district," said Hillsman. "They are focusing primarily on upwardly-mobile homeowners, the affluent, the black bourgeoisie primarily. But the district includes a lot of poorer people in these areas, both black and white."

Miller, a D.C. schools administrator, echoed Hillsman's view of class divisions "in terms of what has been delivered" to the district.

Wynn cites a "strong record of legislative involvement . . . . I sponsored the racial and ethnically motivated crime law. I was also on the conference committees on all the major anti-drug legislation and on the drunk-driving bill."

Miller remains bitter about being dumped from Wynn's ticket after what she said was "an agreement we made we would run as a team." Her exclusion, she said, "took me by surprise, made me question his reliability."

Wynn said he dropped Miller for the same reasons she gives in running against him, her unreliability and her unwillingness to be a team player. For instance, he said, she backed another district's delegate against Ulysses Currie for chairman of the county's House delegation. Currie's loss, Wynn said, "made it difficult for us to get {legislators'} votes for the district."

Wynn complained that Miller "mishandled" an incident in January when a group of high school students she invited to the General Assembly broke into a gospel song to mark the birthday of Martin Luther King Jr. House Speaker R. Clayton Mitchell (D-Kent) had denied her request to allow the group to sing and two weeks later stripped her of a committee assignment as punishment.

Miller complained that Wynn failed to come to her defense. Wynn says the whole flap could have been avoided if Miller had been a better politician.

One point is undisputed. "The race is exciting," said Tignor, who was Wynn's campaign manager before joining his ticket. "It's competitive."