Constance J. Horner, President Reagan's latest nominee to head the Office of Personnel Management, won the support of the Senate Governmental Affairs Committee yesterday after a generally amiable confirmation hearing that focused primarily on the contentious legacy of former OPM director Donald J. Devine.

Horner won praise from senators in both parties, even though she refused to take specific positions on some of the most pressing issues facing the personnel agency -- from revamping the federal retirement system to revising rules for the government's annual charity drive.

Horner also refused to promise -- as some Democrats had hoped -- that she would not become personally involved in the 1986 election campaign. Instead, she said only that she would show "sensitivity," and asked senators to rely on "my conduct today and my reputation" as their guide.

The Democrats were hoping to avoid the kind of controversy that Devine stirred when he delved head-first into the 1984 campaign on behalf of conservative Republican candidates.

"Should the head of the Civil Service -- and that will be you in a matter of hours -- be at the political barricades?" asked Sen. Thomas F. Eagleton (D-Mo.).

Horner pointed out that the Hatch Act, which prohibits civil servants from engaging in partisan political activities, does not apply to the director of the OPM. "I make a distinction between the Civil Service and the head of the Civil Service," she said.

"And nobody can give off the aroma of the Civil Service better than numero uno," Eagleton said, reminding her that she owes her job to Devine's having been forced to withdraw his nomination to a second four-year term.

Horner promised to tone down the rhetoric about federal employe issues, which became increasingly vituperative during Devine's tenure. She also said she would work to rebuild the damaged morale of the professional Civil Service by taking the time to explain Reagan administration policies and avoiding "the cheap shots."

Yesterday's hearing suggested that if Horner is confirmed, as expected, the tone at the OPM will change, even if much of the substance remains the same. "I don't look forward to using highly personal attacks," she said.

After the hearing, Sen. Ted Stevens (R-Alaska), who chairs the panel's Civil Service subcommittee, said he expected that the Senate would vote on Horner's confirmation before its August recess begins Friday.

Horner said that the hearing had produced no surprises and that she expected to be confirmed quickly.

Horner, an associate director of the Office of Management and Budget, is regarded as a low-key, pragmatic administrator, and her nomination was seen by many as an effort by the White House to steer clear of controversy. Still, she is well liked by many of the New Right conservatives who are loyal to Devine.

One of the first and most politically sensitive issues that may face her at the OPM could be the drafting of new regulations for the Combined Federal Campaign, the government's annual charity drive.

The Reagan administration has tried to limit the drive to "traditional" charities, and to keep out political-advocacy and legal-defense groups. On July 2, the Supreme Court ruled that the OPM could exclude groups to keep the drive manageable, but asked a lower court to review the office's motives for excluding certain groups.

Although the OPM previously had announced that it would not change the rules for this year's campaign, some charities are concerned that Horner may try to rush through revisions. The National Committee for Responsive Philanthropy has said changes now could "jeopardize" the fall campaign and disrupt charities that have been following the old rules.

In response to a question, Horner said she will seek legal advice on whether the rules can be changed in time for this year's drive.