Incumbent Democrat Winfield M. Kelly Jr. is still trailing Republican challenger Lawrence J. Hogan, in the Prince George's County executive's race, according to separate polls released yesterday by the candidates, but the margin of Hogan's lead differs markedly in the two surveys.

A polls conducted for Hogan on Sept. 21-22 showed Hogan holding a 56 to 32 percent lead over Kelly with 9 percent undecided. Hogan said the results of his latest poll were almost identical to that of a poll taken two months earlier and indicated "a strong unlikelihood" that Kelly could catch up before the Nov. 7 election.

According to a poll conducted for Kelly, however, Kelly is trailing by only 41 to 35 percent with 24 percent undecided. Kelly said his poll, taken Sept. 25-28, showed that he was making "significant movement" and he predicted that he would overtake Hogan by election day.

Kelly, in an interview yesterday with Washington Post reporters and editors, said that he has been knocking on doors almost every night for the last two moments and has noticed "the trend going in my direction."

"I've been preparing for a race against Hogan for four years," Kelly said. "We've been doing polls on him all that time. Hogan started with a 12-point lead and now we've got him down to six. I think we can make up those six points." He dismissed the Hogan poll showing him trailing by 24 points as "simply wrong."

Kelly, the 42-year-old milionaire who upset incumbent Republican County Executive William Gullett in 1974, said that Hogan, a former three-term congressman from Prince George's, was the only politician who had a chance of beating him this year.

"I would have beaten the brains out of anyone else," said Kelly. "But Larry's very popular from his days in Congress. He's a great PR (public relations) guy. He's done a good job of selling himself."

Kelly accepted his underdog status in the race by conceding that "it may be" that county executives cannot be re-elected to a second term. "The demands are insatiable," he said. "The negatives attached to me this year are the negatives attached to anyone who holds this job." Then Kelly added whimsically:

"I think I ought to go back by acclamation.The people ought to put me back - I'm so good."

But Kelly indicated that he would not be too depressed if Hogan beats him. "There are a lot of things I'd like to do with my life," said the man who made his fortune in the food wagon business. "In fact, there are times when I wonder why I'm in politics this long."

Kelly, who often likens his position to that of a corporate manager, said his top priority in a second term would be to adjust county government to the anti-property tax climate that is so much in evidence this year.

"I'd like to follow through on the tax cuts we effected this year and keep the budgets down to 4 percent yearly increases," said Kelly. "I'd also like to bring together the operations of various agencies to eliminate the duplication of services."

The county executive said that Prince George's, under his tenure, has rid itself of an inferiority complex, reduced the racial tensions that split the suburban region in the early 1970s, and undergone an economic development boom "greater than at any time in its history."

"Prince George's is coming close to being a model place, he said, in reference to the county's black-white relations. "When the blacks come in the whites don't run like they used to."

Kelly said that in order to attract major industries to the county he has pushed for "housing opportunities for wealthier people" and eliminated the construction of middle-and low-income garden apartments. "I get criticized for that - worrying about rich people - but they are important for the tax base."

Although the county's police union has endorsed Hogan and given a vote of no-confidence to Kelly and Police Chief John W. Rhoads this year, Kelly said he considered himself "a strong supporter of the police."

"John Rhoads has done a great job and is going to be the chief for four more years," said Kelly. "I understand it's difficult for many policemen when they've been told for so long to react one way and then are told: 'Fellas, the game's changed. You're no longer the long blue line standing between the county and the hordes coming in.'"

Of all the disaffected interest groups in the county, Kelly said, the most opposed to his reelection appear to be the apartment tenants. For two years of his administration, Kelly imposed a county renters tax, a measure that was not accepted warmly by the tenants who make up about 40 percent of the county's population.

"That feeling of kind of picking on tenants has kind of permeated through my (tenure)," said Kelly. "They think I'm a mean guy, mean guy."