Powerful veterans groups appear to be successfully sandbagging the Carter administration plan to wipe out special hiring and tenure benefits for military veterans in the bureaucracy.

A phase-out of "veterans preference" is a major section of the president's civil service "reform" bill now in Senate and House committees. While it appears the White House will get most of the reforms it wants to streamline hiring, firing and the executive corps of government, the idea of eliminating veterans preference looks dead in the Senate and is on the critical list in the House.

Earlier this week, the Senate's Governmental Affairs Committee voted to leave veterans preference intact. It was the first major setback in Congress for the Carter concept of civil service reform.

It now looks like the House-Post-Office-Civil Service Committee will follow suit, and leave veterans preference alone when it writes its version of a civil service reform bill. But the administration is lobbying hard with Democrats, promising campaign help for members who want it and promising not to help members who think reelection would be easier if they are not tied too closely to Carter.

Rep. James Hanley (D-N.Y.) is planning to introduce an amendment barring any changes in veterans preference. He's next in line to be chairman of the committee, and can count on a solid bloc of Republicans and more than enough Democrates to vote with him.

Under the Veterans Preference Act of 1944, military veterans get five points added to test scores. Disabled veterans get a 10-point preference. Those points don't help in promotion, but they do give veterans more security during layoffs than nonveterans.

Administration officials who want to phase out veterans preference rights (except for disabled veterans) argue that the hiring and retention preference gives white male special lifetime breaks within the civil service.

Approximately half the federal work force is made up of military veterans. government officials say, against a figure of 25 percent for the veteran total in the general work force.

Officials say that 41 percent of the people passing college-level entry exams for government jobs in 1976 were women, but only 31 percent of the people actually hired were women. Veterans accounted for 19 percent of those who passed the same tests but 29 percent of the people hired were military veterans.That, the White House says, is proof that the veterans perference laws often exclude the best people who want to come into government.

White House aiders say it will be very difficult for women and minority males to graduate to top-paying "supergrade" federal jobs at the $42,000 to $47,500 range, because the mid-level "feeder pool" they are drawn from is 94 percent white male and 65 percent veterans.

Administration officials have promised to fight for exculsion of veterans preference on both the Senate and House floors. But the Senate isn't about to tackle the controversial change in an election year, especially because liberal Alan Cranston (D-Calif.( the Senate's expert on veterans affairs, is opposed to any major change in veterans preference benefits.

Competent congressional insiders believe there is a good chance both the Senate and House would go along with a proposal to eliminate veterans preference for members of the proposed senior Executive Service. The SES. part of the reform package, would set up a new hiring, promotion, compaensation and firing system for Uncle Sam's 9,200 top employes.

Eliminating veterans preference in the SES would represent a foot in the door in the battle to eventually scrap veterans preference at other levels of employment. But that big step won't come in this election year because of the effective lobbying job done by organized veterans groups.