President Reagan, saying Virginia needs Wyatt B. Durrette's "strong, principled leadership," embraced the Republican candidate for governor yesterday at a Northern Virginia fund-raising luncheon that will give the GOP about $500,000 for critically needed television advertising.

In a 13-minute speech on behalf of a campaign that is trailing in the polls, the president stressed the themes of economic growth, law enforcement and family values that Virginia Republicans have made central to their campaign. And Reagan added some of his own, decrying rock music and the media for their "glorifications of drugs, and violence, and perversity."

The president, who was whisked from the White House to a Crystal City hotel in a 12-car motorcade, joked that he didn't have to travel far to show his support for the Virginia Republicans.

"I've just come a short distance to be here today, but I feel worlds away from that town across the river," he told the crowd of about 450 at the $1,000 per plate fund-raiser for Durrette. "I'm here today to tell you that America needs him, too, because it's only if we pull together at both the state and national level that we can give America the bright future of expanding hope and opportunity she deserves."

Durrette, who began speaking as Reagan was led from the room, praised the president as a leader who "has brought a nation back to life" and said the Republican Party "is on its way to becoming the majority party of America and of Virginia."

The luncheon at the Crystal City Marriott Gateway, originally scheduled last July in Richmond but postponed because of Reagan's cancer surgery, was a long-awaited fund-raising and media event for the GOP campaign. It has been hampered by strategy disputes and an inability to match the TV advertising of Democrat Gerald L. Baliles.

A Washington Post poll published yesterday showed Durrette trailing Baliles by 50 to 31 percent in the Nov. 5 general election. The poll, which indicated many voters are not interested in any of the three statewide races, also showed Baliles' running mates for lieutenant governor and state attorney general in commanding leads over their GOP opposition.

Although the poll was not mentioned in any speeches at yesterday's luncheon, it preoccupied much of the crowd and drew critical comments from Durrette who was besieged by supporters and reporters asking about it. "I think the adjective, ridiculous, describes it pretty well," he said.

In his speech, Durrette turned to his wife, Cheryn, at the head table and his three daughters and 6-week-old son, and described the campaign as a "family enterprise" and added: "We so desperately need your help."

Some Republicans, saying Durrette is trailing, questioned whether their entire ticket is trailing by as much as the Post poll said.

Former U.S. senator Harry F. Byrd Jr., a staunch conservative who endorsed Durrette Tuesday, agreed with the poll's findings that few voters are showing interest in the campaign and said in his hometown of Winchester "the enthusiasm is greater for the other side."

Republican National Committeeman William Stanhagen of Manassas said, "I don't think we're that bad," but allowed, "There's certainly a danger when anything looks like a runaway." He said the poll would likely motivate some GOP activists but could hurt Durrette among less interested voters.

Durrette also dismissed a report in Newsweek this week that some White House aides have "all but written off" Durrette's chances and were reluctant to have Reagan too closely identified with Durrette. Terry Wade, a spokesman for the Republican National Committee, rejected the magazine's item as "absolutely not accurate."

In addition to the funds raised by the luncheon, Pennsylvania Gov. Richard Thornburgh donated $75,000 to Durrette from the Republican National Committee. Durrette consultant Edward DeBolt said the RNC has donated about $200,000 in cash and about $200,000 in services to the campaign.

Most of the money raised yesterday is expected to fund TV commercials for Durrette, including some shot during the luncheon yesterday. The luncheon followed a $10,000 per person reception where dozens of contributors stood in line to have their picture taken with Reagan.

Some of the money -- aides said they were not sure how much -- is expected to go to state Sen. John H. Chichester, the Republican candidate for lieutenant governor, and W.R. (Buster) O'Brien, the GOP's nominee for state attorney general