Prince George's County Democrats have finally reached a tentative agreement on who will be endorsed for the Sept. 9 primary.

The county's eight state senators and County Executive Parris N. Glendening settled last week on the names and faces to appear on the "ticket," a brochure listing the candidates endorsed by the county's dominant Democratic faction.

The ticket is the subject of anxiety, lobbying and jockeying in the months (and years) before an election, for it is believed to hold the key to electorial success in Prince George's, especially in less-visible local races. But the endorsement is also coveted by statewide candidates because it is made by the county's largest political organization.

Always a source of controversy, negotiations over the ticket were complicated this year by the deep divisions over the gubernatorial and state's attorney races and, to a lesser extent, the U.S. Senate race.

The solution? To form "topless tickets" in which local candidates would endorse each other but leave off endorsements of the top statewide races.

The final decisions, according to Glendening, are:In six out of eight legislative districts -- all those except the Clinton-based 27th of Sen. Thomas V. Mike Miller Jr. and New Carrollton-based 22nd of Sen. Thomas P. O'Reilly -- the tickets will be topless as to the governor's race.

In the 27th and 22nd districts there are a number of party regulars who support Baltimore Mayor William Donald Schaefer's candidacy, so he will appear on the ticket. In the others, officials are divided between Schaefer and Attorney General Stephen H. Sachs. If they choose, they can print separate brochures listing their respective endorsements in that race.

* In the state's attorney's race, Democrats in six out of eight legislative districts have agreed either to support challenger Alex Williams or no one. In the other two, again the 22nd and 27th, the literature will endorse incumbent Arthur (Bud) Marshall.

* The Senate race remains up in the air, so officials decided to go ahead with an initial printing without any endorsement until they can make up their minds.

All this is a rather stark change from years past, Glendening noted. "We are in a very decentralized process," he said. "It's different." Unions Split on Candidates

Maryland's two public employes' unions are split over whom to support for the Democratic nomination for governor, a division that could weaken their clout in the upcoming primary.

The state branch of the American Federation of State, County and Municipal Employees announced last week an endorsement of gubernatorial candidate Stephen Sachs. The group expressed "shock and concern" that the Maryland Classified Employees Association had opted to support Mayor William Donald Schaefer.

Bill Bolander, spokesman for AFSCME, said the two unions have disagreed in the past, but he said MCEA's endorsement of Schaefer was too much to overlook.

"It's inconceivable that MCEA would support two such men as Schaefer and Melvin Steinberg," Bolander said.

Steinberg, Schaefer's running mate, helped ram through the General Assembly legislation that altered the state's pension formula, decreasing benefits to tens of thousands of public employes, Bolander said.

"Through the pension legislation," he said, "employes suffered additional money taken from their paychecks to keep their benefits. Many couldn't afford this and were forced to change to pension plans with less benefits."

Joe Adler, MCEA's executive director, said the legislation was unfortunate, "but that was in the past" and their endorsement is "not so much for Steinberg as it is for Schaefer. You can't separate lieutenant governor from governor."

The MCEA endorsed Schaefer, Adler said because city workers received pay raises each year the mayor has been in office. Schaefer won the endorsement by a 2-to-1 margin in a poll of about 700 MCEA members, Adler added. While the two unions represent the same types of employes, Bolander said, "MCEA has always tended to have a much more pro-management view. They have been an office type, social type of organization. We question how much support they have for employes.

"Sachs cares about working people," he said.

The division between the two unions is likely to reduce the influence public employes have in the gubernatorial race because the supporters -- with their campaign contributions and volunteer time -- are likely to cancel each other out. Press Conference Competition

It was dueling press conferences Monday when Republican Senate contenders Linda Chavez and Richard Sullivan held simultaneous briefings for reporters to announce their plans for improving U.S. exports and reducing the trade deficit.

Spokesmen for both candidates said the announcements had been scheduled "for weeks," and each side suggested that the other was not above moving the date of his or her conference to compete with the other's.

Nevertheless, both agreed that, as Chavez put it from her announcement at the World Trade Center in Baltimore, "free and fair trade is in the best economic interest of the citizens of the United States." And both maintained, as Sullivan said from his podium in front of the U.S. Capitol, that the "the most effective approach to solving our trade problems lies in creating the fear of retaliatory economic actions" against countries that refuse to allow U.S. imports.

Another specific suggestion from Chavez was legislation to protect U.S. patents, copyrights and trademarks, including action that would ease protection U.S. law gives to software products produced by countries that fail to protect U.S. products in kind.

Some of the "Sullivan Solutions" include proposals to hire more customs agents so the United States can better enforce fair trade laws and abolish laws that "hamper America's ability to compete," such as corporate average fuel economy standards for automobiles. Debate Replay

Baltimore radio station WBAL had so much fun with its gubernatorial debate last week that it's going to rebroadcast it.

The debate -- which featured a surprise appearance by Baltimore Mayor William Donald Schaefer and verbal fireworks between the mayor and opponent Attorney General Stephen H. Sachs when Schaefer left halfway through -- will be aired today at 8 p.m. on 1090-AM.