If he had it to do over again, the head of the 2 million member AFL-CIO coalition of federal, postal and state government worker union says he would not endorse Jimmy Carter for president.

W. Howard McClennan, president of the big and influential Public Employees Department of the AFL-CIO says he and his members have been completely disenchanted with Carter. He says the president has backed off on promises to support equal government-industry pay, vetoed a reduced workweek for firefighters he promised (August 1976) to sign, and has not pushed political reforms of the Hatch Act with vigor.

McClennan's bitterness towards the Carter presidency is more significant than that of a one-issue union chief unhappy with a Democratic president. He sits on the AFL-CIO executive council, is president of the militant Firefighter Association and enjoys the good will of fellow Bostonian Thomas P. O'Neill to whom McClennan gave his first job. O'Neill, a one-time grocery stock boy, currently is speaker of the House.

In a session with reporters yesterday, McClennan said Carter "looks like a one-term president." He said he would have a hard time supporting Carter if he runs again. He stopped short of saying he would endorse a Republican for the top office, but said he would advise members to "sit it out" if the 1976 election were rerun today.

The PED can muster a formidable array of lobbyists on Capitol Hill, and provides even more important financial and human resources during key elections. The AFL-CIO unit believes it was instrumental in giving Carter his margin over former president Ford.

McClennan said the days are "gone" when federal and postal unions within the AFL-CIO automatically endorse Demoscratic candidates. When requests for financial assistance come in now, he said, his office "checks the record" to see whether handout-seeking politicians are worthy of the purchase of a bloc of tickets to fund raisers, other financial assistance from unions or all-important doorbell-ringers and grass roots supporters that are organized labor's ultimate weapon.

McClennan said fellow union leaders are raging over Carter's "hard line" toward civil servants. With organized labor in government cool toward Carter, and the White House planning various unpopular (to the unions) changes in pay and pensions, McClennan predicts 1979 will be a "very tough" year for the average fed. If so, he predicts the 1980 year could be "very rough" for Carter.

Retirement Pay Changes: The Federal Times today reports that the Carter administration is thinking about eliminating one of the two annual cost of living raises for U.S. workers. The weekly newspaper says administration sources believe they could save millions each year if retired federal and military personnel were held to one cost-of-living increase annually. Currently retirees get two raises - in March and September - to keep pace with the cost of living.

Andy Biemiller, perhaps the nation's most influential and durable lobbyist, will retire shortly as head of AFL-CIO's legislative department. He's had the top job since 1956, was a two-term member of Congress from Milwaukee (a Democrat) and is credited with putting the union label on virtually every piece of social welfare legislation of the past three decades. Biemiller, 72, will be succeeded by his 51-year-old assistant Ben Young. Young is a veteran of the AFL-CIO Capitol Hill cadre, working as a legislative representative before becoming Biemiller's deputy seven years ago.

The Best: National Civil Service League has given its prestigious awards - for outstanding career service - to 10 of the bureaucracy's best. Winners are John F. Blake, deputy director of the CIA: Ann Z. Caracristi, cryptology expert at the National Security Agency; Julius L. Katz, assistant secretary of State; William E. Lilly, comptroller of the spaceagency; Peter G. McCabe, chief of magistrates, U.S. courts; Thomas S. McFee, HEW's super-level personnel chief; George J. McQuoid, deputy executive director of the Civil Service Commission; Edward G. Sanders, deputy associate director, Office of Management and Budget; Dorothy L. Starbuck, benefits director of the VA, and William E. Williams, deputy commissioner, Internal Revenue Service.