PRESIDENT CARTER'S PROPOSED revision of the laws governing civil service was-when he sent it up to Congress last winter - a pretty ambitious thing. As might have been expected, it has been revised downward and made more modest in some respects by legislators. Senate, provisions that would have eliminated extravagant preferential treatment of veterans have been removed. A House committee has been altering the measure with a view to making it more agreeable to labor groups, mainly by tightening up its various protection of employees.

This, of course, has been done pretty much at the expense of the president's effort to give administrators in government a stronger hand in managing civil-service employess. But no one supposed the legislators in either the Senate or the House would merely rubber-stamp the administration's proposal, and the changes made thus far have seemed to be well within the range of the kind of final negotiation between Senate House and administration that could lead to a genuinely good and useful reform bill.

We say "thus far," because now, in the House, the affair has taken a turn that may prove fatal to civil-service reform of any kind this year. A group of Democrats in the House Post Office and Civil Service Democrats in the House Post Office and Civil Service Committee has appended to the bill the even more sensitive and controversial legislation aimed at overhauling the Hatch Act. This legislation, which would reduce the prohibitions against federal workers' becoming involved in political activity, is greatly favored by the unions and passionately opposed by large numbers of Republicans-and the upshot is that with the Hatch Act legislation stuck onto the civil-service reform, the Republican support for civil-service reform largely vanishes.

Although we ourselves do favor a liberalization of the Hatch Act's restrictions on federal workers' political rights, the joining of these two measures-to the ultimate defeat of both-strikes us as a pointless and damaging act. It's not as though the civil-service reform minus the Hatch Act provisions were and incomplete change, one that required the Hatch revisions for purposes of fairness or equity. The civil-service reform can stand on its own. With the freight of the Hatch Act liberalization it almost certainly will collapse. There is not much time to undo the unfortunate handiwork of the Post Office and Civil Service Committee in this respect - at least not if there is to be legislation this year.It will be a grimly ironic outcome to a large Democratic promise, if members of Mr. Carter's party in Congress contrive to sabotage his sound (and politically popular) effort to make the bureaucracy work better-especially when that effort, unencumbered by Hatch legislation, stands a good chance of enactment.