The Senate gave President Reagan his first veto victory of the year yesterday as it ducked a showdown vote on legislation that would have forced continued enforcement of the "fairness doctrine" requiring broadcasters to present conflicting views on key public issues.

Lacking the two-thirds majority needed to override Reagan's veto of the measure last week, the Democratic-controlled Senate voted, 53 to 45, to send the legislation back to the Commerce Committee, where proponents have indicated they may attempt to revive it at some point.

But the clear message was that "the veto would have been sustained," according to Sen. Bob Packwood (R-Ore.), principal opponent of the legislation. "Clearly it was not in the interests of the Democrats for the president to win" a clear-cut showdown over the veto, he added.

Reagan has vetoed only three measures this year, and Congress overrode the first two: clean-water legislation and a bill to reauthorize highway and mass transit programs. With both houses in Democratic hands for the first time since Reagan took office, Democrats seized on the veto-override votes as evidence of a Democratic resurgence in defining national priorities.

But the fairness doctrine did not have the same lure as money for water-cleanup and highway-building efforts, and the Senate fell short of a two-thirds vote when it initially passed the bill, 59 to 31, two months ago.

The House had approved the measure, 302 to 102, and was expected to vote to override the veto. But a two-thirds vote of both houses is necessary to enact legislation over a presidential veto, making the Senate action tantamount to sustaining the veto.

The fairness standard has been in effect since its adoption by the Federal Communications Commission in 1949 and was thought to have the force of law until last year when the U.S. Court of Appeals for the District of Columbia held that the FCC could repeal it without congressional approval.

The legislation was aimed at preventing the FCC from repealing the rule, and Congress' inability to enact it over Reagan's veto appears to leave the commission free to do so.

In his veto message Saturday, Reagan said the doctrine violated broadcasters' First Amendment rights. "This type of content-based regulation by the federal government is, in my judgment, antagonistic to the freedom of expression guaranteed by the First Amendment" and long considered unacceptable for any other kind of journalistic activity, he said.

But supporters of the doctrine argued that it has encouraged presentation of opposing viewpoints in an electronic medium that is at least partially limited in the number of outlets.