The narrow driveway of the downtown Holiday Inn was transformed - a red-carpeted platform and a three-piece combo on one side, another platform for television cameras on the other. In between, about 100 John Warner supporters wearing white sailor caps decorated with "W" in red glitter on the brim awaited their candidate - and his wife.

"Virginia is for lovers," said one-time candidate for lieutenant governor George Shafran in introducing Warner. "And here he is: Lover Number One."

Warner's rally was but a sideshow in the two-day Republican convention that opened here yesterday. In what is being described as the largest political convention ever held in this country, some 9,700 delegates and alternates will participate in what may be a lengthy meeting to choose a man to run for the U.S. Senate. The current senator, William L. Scott, is retiring to "devote more time to my family" and resume his law practice, and the Republicans here intend to hold on to his seat.

The real action won't begin until this afternoon when the nominating process begins. Yesterday was for registering, checking into hotels, greeting old friends, listening to reports from various leaders and national party chairman William Brock, and looking around.

More than 100 press representatives, including some from the British Broadcasting Company, the San Diego Union and two of the three television networks, are covering this meeting, a dramatic change from 10 years ago when the entire convention was about the size of today's 1,500-member delegation from Fairfax County.

There are squads of teen age pages, 30 hostesses, and intercom system to communicate with podium from the stands and plenty of what is called "security."

Fourteen off-duty Richmond police officers are on hand as guards and special passes are required to go anywhere in the coliseum. Each campaign also has its own identification passes to prevent spying; Warner's, for example, has three different laminated badges denoting varying levels of access to the candidate.

Although Warner has the most lavish media operation of any of the four candidates, with three kinds of buttons, press kits and the attention riveting presence of his wife, Elizabeth Taylor, he is only one of three candidates given a shot at winning the nomination.

Former Gov. Linwood Holton claims to be in second place behind acknowledged frontrunner Richard Obenshein, but both Warner and Holton said that Obenshein's strength will peak early and then diminish. A fourth candidate, 35-year-old state Sen. Nathan Miller is spoken of with great affection as "a man of the future."

Miller has gotten quite a bit of approval for what one supporter calls "the most brilliant piece of political literature" - an imitation of Time magazine featuring him on the cover. The four-page glossy brochure features "stories" about Miller and a schedule of campaign events.

The biggest spontaneous greeting of the opening day went to noncandidate, noncitizen Taylor. When she entered the coliseum wearing a sailor cap and a red and white striped shirt emblazoned with the slogan "I'm in Warner's corner," the business of the convention was interrupted by applause that clearly was directed at the movie star rather than her husband.

Warner acknowledged as much, joining the crowd in applauding his wife, who responded by waving both of her hands over her head.

Yesterday, in between the applause, the speeches and the greetings, the talk was mainly on three topics: who was going to win, how long the convention will last, and how many people may show up. Only about half of the expected delegates and alternates had registered by late yesterday afternoon.

Several candidates are saying that the length of the convention could effect the outcome. With so many people voting, it may take as long as two hours to count one ballot and some delegates may be bored or tired and leave if the meeting goes on too long. "(The outcome) may depend on who's here," Warner said.

Brock, whose term as national GOP chairman has been marked by his effort to attract blacks, young people and other minorities to the party, was applauded by the handful of black delegates here when he noted that "in America today if you're a black, or young, or female, you know for sure that you are going to be the last one hired and the first one fired. . . ."

Decrying "bossism," Scott declined to take a role in choosing his successor. He said only that a conservative should be nominated "because Virginia is a conservative state."