A new rating system coming from the governments biggest union will jolt many politicians courting the elusive, important bureaucrat-voter bloc. It represents the nation's best-paid, best-educated "minority" group.

The bread-and-butter test being devised by the American Federation of Government Employes (nearly 300,000 members) will surprise some liberal Democrats who think endorsement from the AFL-CIO is enough to get government union support. And it will help some Republicans, like Maryland Sen. Charles Mc. Mathias and Rep. Majorie Holt. They come out with better ratings than more liberal Democrats like Virginia Rep. Joseph Fisher or Missouri Sen. Tom Eagleton, whose concerns about government retirement costs concern some government retirees.

AFGE President Ken Blaylock said the ratings when published, will sometimes put the federal union in conflict with its fellow AFL-CIO groups' political endorsements. "But the first duty of a union is to look out for its own members," Blaylock said, indicating that a good COPE endorsement from the AFL-CIO will not automatically help senators or representatives win AFGE's good will.

(There is considerable disagreement as to the size, influence and indeed existence of a "bureaucrat" voting bloc. The numbers are impressive. There are 2.7 million federal white-collar and postal workers and another million retirees. Add to that an even larger military establishment. If you want to count spouses and those with interests in federal pay, fringes and working conditions, double or triple the numbers.) State and local government employes -- who often use federal pay and fringe gains to demand raises an job improvements -- total more than 13 million.

The Maryland and Virginia suburbs aren't the only communities dominated by the workers who are employed by Uncle Sam. Hundreds of communities across the nation revolve around military bases. Ogden, Utah, is -- thanks to the presence of the IRS -- a civil service town like Washington. Bremerton, Wash., Anchorage, Hutnsville, Ala., Columbia, S.C., Knoxville, Tenn., Long Beach, Calif. -- to name a few -- are big government towns.

Philadelphia has 70,000 federal workers; New York City, 110,000. Tinker Air Force Base outside Oklahoma City is perhaps that state's largest employer. Everybody who works there is old enough to vote. The country's biggest white-collar operation is the Social Security Administration at Baltimore.

AFGE's political rating system will give extra points to members of Congress -- or candidates -- who vote "right" on pay raise issues, to block merger of civil service retirement with social security, and who oppose the president's pay reform plans as now written.

Overall good "labor" records and "liberal" voting patterns will help in the political ratings, but not outweigh basic federal-employe items. Example: Under the AFGE rating system, Glaylock said, conservative Marjorie Holt comes out looking better than liberal Joseph Fisher. Blaylock said that "Holt voted right five times on Fisher amendments that were wrong" from AFGE's point of view.

Sen. Orin Hatch (R-Utah), who rarely expects labor support, "voted 100 percent right" on federal pay matters, according to the still-incomplete AFGE study. Similarly, Blaylack said "personal observations" by himself and other AFGE national officers would be used to add or subtract points from individual ratings.

Examples of two Republicans who will stand tall in the AFGE ratings are Sens. Ted Stevens of Alaska and Mathias. Blaylock said their records from a labor standpoint are "not great overall."

"But on the gut issues, where fairness counts, we can depend on them not just to vote, but to fight for us," Blaylock said.

Lest it sound like a GOP tilt for the giant union, be advised that Blaylock has indicated he will probably urge the national executive board to back the Democratic presidential nominee later this summer. When the union meets in Hawaii in August, he expects to ask delegates to endorse a Democrat for president.

Other federal and postal unions are also watching and ranking local and national candidates. The National Treasury Employes Union is in the camp of Sen. Edward M. Kennedy (D-Mass.) thanks to an early endorsement by NTEU President Vincent L. Connery. The National Alliance of Postal and Federal Employes, which bills itself as the nation's "largest, oldest, black-controlled union," has lined up behind Jimmy Carter.

The independent National Federation of Federal Employes has sent questionnaires to each of the major presidential candidates asking where they stand on issues.

The major candidates -- including the White House resident -- will, as always, run against bureaucracy. And Washington. But some of their numbers-people are urging them not to include civil servants or their unions in jabs at big government.