If there is a federal employe voting block -- or if one can be created -- it could tip the balance of power in close primary or national election fights in many states. Both the Carter and Kennedy camps are aware of the numbers.

At least 20 states have more than 50,000 federal workers. Some -- New York, California, Texas, Maryland, Pennsylvania, Illinois, Virginia, Ohio and the District of Columbia -- each have more than 100,000 federal civil servants. Nearly all are of voting age.

President Carter may have lost Chicago Mayor Jane Byrne to Kennedy, but the city has 69,000 federal workers who are, more or less, independent of the powerful Democratic machine.

Although federal and postal workers are partially insulated from partisan politics by law, they represent a highly educated, well paid voting-age group. Studies have shown they vote in higher numbers than many other worker-blocs, though not necessarily in a bloc. Some politicians dream of changing that.

Tantalized by the numbers, Carter and Kennedy staffers are working hard to win endorsements of union leaders representing the 2.7 million federal workers and their families. They are also eager to woo the 1.6 million federal retirees who -- like most senior citizens -- have a very high turnout at elections.

Consider some of the numbers: New York state has 166,000 federal workers; Ohio, 97,000; Texas, 149,000; Oklahoma, 48,000; Pennsylvania, 127,000; Illinois, 103,000; Florida, 87,000; Washington state, 57,000; Virginia, 142,000; Maryland, 133,000; Georgia, 75,000; Alabama, 60,000; Massachusetts and Michigan, 57,000 each; Missouri, 66,000; New Jersey, 69,000; Tennessee, 57,000.

The actual size of the federal-postal bloc vote is anybody's guess. But the government health insurance program has between 6 million and 8 million covered employes and family members.

In states with relatively small populations, the federal bloc vote could have an even greater impact: Kentucky has 35,000 U.S. workers; Hawaii, 30,000; Utah, 35,000; Colorado, 48,600.

Important centers in California are jam-packed with U.S. civil servants.

Los Angeles has 66,000; San Francisco, 64,000; San Diego, 34,000; Sacramento, 25,000. Smaller areas -- like Oxnard and Vallejo have 30,000 federal workers.

In Tidewater Virginia there are 44,000 U.S. civil servants. The numbers pile up if they can be put together. The District of Columbia suburbs and Baltimore (35,000 federal workers) help pick senators in two States.

Kennedy backers got an important boost Tuesday when the 65,000-member National Treasury Employees Union (NTEU) endorsed him and denounced Carter as "anti-bureaucrat." But powerful and bigger AFL-CIO unions are waiting. The Carter people have not given up hope -- despite discontent over federal pay limits and paid parking -- that they can get the all-important civil service vote.

Carter's chief adviser on the federal work force, Alan K. Campbell, believes federal workers have done well under the president. And the Office of Personnel Management chief will be sallying forth with that message in the months ahead.

Campbell thinks the independent NTEU endorsement of Kennedy overlooks what Carter has done for the bureaucracy. He says that federal pay has risen 20.8 percent in the past three years; that Carter pushed through layoff protection legislation for federal workers and persuaded Congress to authorize work-shift tests that have already allowed "thousands of federal workers to begin four-day work weeks on a voluntary basis."

Campbell says the administration has pushed for improved life insurance benefits, and guaranteed grade and pay protection for civil servants affected by reorganizations. New job safety protections are coming soon, he said.

As to the charge that Carter is "antibureaucrat," Campbell says the president has never attacked civil servants or the job they are doing. "He has raised questions about the general responsiveness of the bureaucracy, but that was directed at the system rather than the people in it," Campbell said.

Kennedy people counter that his presidency would mean a new era of "respect and esteem" for civil servants. It looks as if government workers are about to be courted, at least until the elections are over.