Four years ago Maryland gubernatorial candidate Harry Hughes had trouble persuading Prince George's County politicians to talk to him. Local newspaper editors forgot about appointments with him and he frequently got lost in the county because no one would show him around.

Prince George's then was forsaken territory. "There was nothing, zilch," Pat Hughes, the governor's wife, recalled yesterday.

But times have changed for Gov. Harry Hughes. His effective use of an incumbent's appointment powers and abiding popularity with the county's heavily Democratic voters have, over the last year, made him the public darling of the Democratic establishment.

If anyone had doubts about this fact, they need only have followed Hughes around Prince George's yesterday, as local party leaders extolled his virtues at one reception after another, introduced him to prominent and wealthy businessmen and escorted him through nearly every area of the county during a 13-hour tour.

So anxious to please were the Prince George's Democrats that they provided Hughes with a huge recreational vehicle, complete with air conditioning, wall-to-wall carpet, microwave oven, well-stocked refrigerator, and at the back, a double bed covered in chintz, just in case the candidate began to tire.

"He has proven himself not only as a legislator and an executive but now as the governor of the state," said U.S. Rep. Steny Hoyer, who ran on an opposing ticket against Hughes in 1978 but was one of several yesterday to apply a thick coat of pro-Hughes campaign rhetoric. "I have no doubt he will win reelection very handily," Hoyer said.

All of this was good, but expected, news for the governor. For the last year he has actively wooed--in his low-key way--members of the Prince George's delegation to Annapolis.

He helped them win a redistricting battle against adjacent Howard County. He appointed one of their own, Sen. John J. Garrity, who lost his seat under redistricting, to a vacancy on the state Court of Special Appeals. He put a potential opponent of influential Sen. Tommie Broadwater on the quasi-judicial Orphan's probate Court. And, according to some county politicians, he is prepared to appoint Del. Robert S. Redding, who is facing a tough race against Sen. Thomas P. O'Reilly, to the powerful Workmen's Compensation Commission.

"He's been very helpful to Prince George's," said state Sen. Thomas V. Mike Miller, head of the county's eight-member Senate delegation and increasingly a power broker in the party organization. In return, Hughes has made it clear to the county politicians that he is expecting campaign help this time around.

In any election year Prince George's, which has a voter registration nearly 4 to 1 in favor of the Democrats, produces about 15 percent of the state's vote. Prince George's, along with Montgomery and Baltimore counties and Baltimore city, are the key areas in Maryland for a successful election. Hughes lost the Washington suburbs in the 1978 primary to the favorite-son ticket of then acting governor Blair Lee and Steny Hoyer, but overcame the deficit in the Baltimore area.

This time around Hughes seems headed for victory in Prince George's and Montgomery counties, at least in the Sept. 14 primary. Polls by the governor's campaign and county politicians show the area to be the strongest statewide for Hughes, a factor attributable in part to his generally favorable coverage in the local press and television.

It is possible the picture could change somewhat: Hughes' main primary challenger, state Sen. Harry J. McGuirk picked up Lt. Gov. Sam Bogley, a popular Prince George's politician, on his ticket. And some county politicians believe the major Republican candidate, Anne Arundel County Executive Robert A. Pascal, might make inroads in Prince George's, despite his party affiliation.

But with polls showing Hughes with an overwhelming lead, and with the governor's "helpfulness" during the last year, the Prince George's Democrats have responded.

A few weeks ago the county's eight senators became the first legislative delegation to endorse Hughes, despite private complaints that he's aloof and too apolitical. The endorsement means that Hughes will appear at the top of sample ballots distributed by the Democrats and at the top of any campaign literature.

The endorsement came after McGuirk, a longtime political friend of several senators, tried to persuade the delegation to withhold an endorsement. Although some of the senators said they believe McGuirk might be a better governor than the incumbent, the effort ran up against political reality.

"I've been out door-knocking and Harry Hughes is a very comfortable name to mention," said Sen. Thomas P. O'Reilly, who initially supported McGuirk. "He's very popular, there's no two ways about it. McGuirk, even with Sam Bogley would have to do an incredible media blitz to even make an impact."

Yesterday, as promised, the Democrats followed up the endorsement with the tour, a political benefit to them and to Hughes.

At an 8 a.m. breakfast with business leaders, Hughes ticked off accomplishments of his administration--efforts in economic development; elimination of fuel-oil tax, and increased aid to subdivisions allowing them to keep taxes down. In midmorning at Upper Marlboro, the county seat, a gaggle of candidates posed for photographs with Hughes.

At the courthouse, the governor offered his hand to everyone in sight, including a well-dressed man in a three-piece suit.

"Hi," Hughes said, before realizing that the man was handcuffed. "How embarrassing," said a sheriff's deputy, who quickly led the man away as the Democrats whisked Hughes off to a brunch, a lunch and receptions.