Maryland's 26th Legislative District used to be a Democratic stronghold in Democratic Prince George's County, home of Democratic golde boy Steny H. Hover and the site every four years of Democratic landslides.

This year has been different. Political event sin the Suitland. District Heights Largo and Kettering ares have become stranger and stranger. The stranger they get, the better the chances look for John Simpson, the strongest of two Republican delegate candidates in the 26th District.

First, there was the surprising defeat of Hoyer, who represented the 26th in the state senate and Blair Lee Ill in the Democratic primary for lieutenant governor and governor.

"Everybody was so disappointed that Steny lost that things were at loose ends for a long time," said Lorraine M. Sheehan, the only incumbent delegate in the race.

"The interest in working for the party went out for a while. It's our job to stimulate it and we're taking steps in that direction," said Dennis C. Donaldson, who finished second in the Democratic delegate primary with the help of the Prince George's Democratic slate endorsement.

Then there is the problem of Francis W. White, the county council member who decided to run for delegate in the 26th after he was dumped from the Democratic organization's county council state. White won in the primary as an independent Democrat, but has since had to face allegations that he was not a legal resident of the 26th District at the time that he filed for the race.

Pushing those charges is one of the Democrats White defeated in the primary, Frank J. Broschart. Last week, Broschart said, he hired two detectives to help him find proof that White is "an illegal candidate." Broschart said he hoped to file a court challenge of White's Democratic nomination by today.

White insists that he has met the residency requirements by living with friends on Thurston Drive in Kettering since separating from his wife in July 1977.

But controversy over the issue continues, thanks in part to Broschart. And Sheehan, who was elected in 1974 and worked on two previous campaigns in the district, says, "This is the first time in a long time that a Republican is going to give us a race. They have never been taken seriously that I remember."

Simpson and fellow delegate candidate Joseph A. Finlayson have not yet attempted to use White's controversy against him, but both sa they are highly encouraged about their chances.

Simpson, 52, an attorney in District Heights who worked in the U.S. Congress for 24 years as a legislative or administrative assistant, says he is hoping that voters' dissatisfaction with poor government services in the 26th will cause voters to switch from traditional Democratic voting patterns.

"Our district has been one of the most neglected and taken-for-granted districts in the county," Simpson said. "I think that for that reason many Democrats are going to be looking for new blood."

As evidence of the district's problems obtaining services, Simpson tells of a sign erected four years ago on Silver Hill Road outside District Heights annuncing the imminent construction of the "Spalding Regional Library" by the county.

The library still has not been built, Simpson says, and the sign, which rotted and collapsed, has been replaced by a new billboard announcing a 1981 opening for the library branch. Meanwhile, he says, both Bowie and Oxon Hill have gotten new libraries while District Heights and Suitland have waited.

Simpson says he will spend at least $4,000 on yard signs, newspaper advertisements, and circulars, but he still had an uphill battle. There are three registered Democrats for every Republican in the district, and despite disappointment over the governor's race, many are working.

Also working against the Republicans, who must hope for a large-scale rejection of the Democratic candidated by Democratic voters, is the variance of interests and issues in different areas of the district, which has changed in the last few years as the percentage of black residents has increased.

"District Heights people talk about taxes," says Sheehan, "but you don't hear much about taxes in other areas. Suitland people talk about the Metro and about revitalization programs for business. They also want that library. And the black community is concerned about recreational facilities inside the Beltway. It really varies from place to place.

White, for one, seemed to be affected by the varied interests of particular areas in the Democratic primary. A former chairman of the Metro board, who fought to keep the proposed Branch Avenue line of the rail system, White carried precincts in north Forestville, Suitland and Kettering heavily, although he trailed Democratic slate members by 4-1 in other areas of the district.

Finlayson, the only black candidate, could benefit from the support of the growing black community, which now makes up between 30 and 40 percent of the population in the district. Finlayson says he would work against what he says is the effort by community leaders to shuttle liquor stores into areas where blacks have moved in.

The Democratic candidate for Hoyer's old senate seat, B. W.(Mike) Donovan, who moved up from the House of Delegtes to run for the position, has no Republican opposition in the general election.