Federal worker unions, traditionally in the flyweight class when it comes to giving political contributions, will pump $2 million or more into November Senate and House races. Most of their financial and moral support will go to Democrats, whether incumbents or challengers.

While their political action committees (PACs) are small compared with those of other labor groups and with big business, the new round of check-writing by government employe organizations will surpass their entire political financial outpourings of the last five elections.

The biggest war chest, so far, has been built up by the National Association of Retired Federal Employees. NARFE's membership has been booming since Congress and the White House began cutting back the federal pension system.

NARFE President Ludwig J. Andolsek said his organization's PAC had about $11,000 in the bank when he took office in January. As of Friday, it had $458,000.75 on deposit. So far, Andolsek said, nearly 27,000 members had sent political donations, and he expects to hear soon from many of the organization's 450,000 other members.

Andolsek, a lifelong Democrat who served at the Civil Service Commission (now OPM) under Presidents Kennedy, Johnson and Nixon, says "we are nonpartisan . . . . we evaluate the candidates and give to our friends" whether Republicans or Democrats.

The American Federation of Government Employees, which plans to spend $400,000 on congressional races this year, has decided to be more partisan.

Asked if the AFGE is supporting any Republicans this year, President Kenneth T. Blaylock said only one: Maryland Sen. Charles McC. Mathias. Mathias is not up for reelection this year.

Blaylock said candidates who get a Triple-A rating from his union will get the maximum $10,000 donation -- half for the primary and half for the general election. In Northern Virginia, he said, the AFL-CIO union is supporting Ira Lechner and Herb Harris, who are trying to unseat Republican incumbents Reps. Frank Wolf and Stan Parris. In Maryland, it is supporting Sen. Paul Sarbanes and Reps. Steny Hoyer and Mike Barnes, all Democrats.

David Gusky of the independent National Federation of Federal Employees said his union hopes to spend between $50,000 and $100,000 on the fall races. NFFE's political spending will be bipartisan, he said, but there is "no question that Democrats tend to support the interests of federal workers" better than Republicans.

National Treasury Employees Union, another independent, hopes to spend $250,000 on the elections. Union official Jerry Klepner said "98 percent of our PAC money has gone to Democrats" but it has also helped New York Republican Reps. Bill Carney and Norm Lent, and gave to the unsuccessful primary fight of Rep. Edward J. Derwinski (R-Ill.).

NTEU has helped local Maryland Democratic incumbents, and is also supporting Lechner and Harris in Virginia.

The two major postal unions, the National Association of Letter Carriers and the American Postal Workers Union, each have six-digit PACs leaning heavily toward the Democrats.

Republicans in big federal employe population centers are trying to put as much distance as possible between their campaigns and the Reagan administration. Many feds are furious over pay caps, RIFs, pension delays and a possible new round of furloughs because Reagan vetoed the supplemental appropriation last week. They will also begin paying a 1.3 percent Medicare tax next January.

The union leaders are split over whom to support for president in 1984 (split, that is, between Democrats Edward M. Kennedy of Massachusetts and former vice president Walter Mondale).

Union leaders also agree that President Reagan is the best organizer they could have, and best-fund-raiser the Democrats could hope for among government workers. "With an enemy like that," one said, "who needs friends?"