STAUNTON, VA., DEC. 5 -- Republican presidential candidate Marion G. (Pat) Robertson, shaking Virginia's GOP to its core, today sealed an impressive straw poll victory and public relations bonanza after 1,000 of his supporters descended on a party convention here.

"We're going to invade the Ingleside in a few moments," Robertson told a chanting crowd shortly before their caravan of buses, trucks and cars slowly made its way to the Ingleside Inn, site of the Virginia Republicans' fourth annual winter meeting.

Robertson's victory in the presidential preference ballot, which was all but assured since his rivals for the 1988 Republican nomination had written off the event, was not nearly so impressive as his show of sheer political strength today. The evangelist's ability to mobilize voters from every corner of the state awed, and in many cases dismayed, even the most hard-bitten veterans of the Virginia GOP's infamous internal wars.

"The party regulars are scared," said Carl Bieber, one of the few party officials who attended the revival-style rally for Robertson a few miles from the convention site.

"It's just an awesome display," added Don Moseley, another member of the state Republican central committee. "Those are very committed people, and they're not going to go away."

For an often-fragmented party that would dearly love to retain an open U.S. Senate seat next year and recapture the governor's office from the Democrats in 1989, Robertson's flair for organization in his native Virginia might be a welcome tonic. Indeed, several speakers who addressed the Robertson supporters today -- Paul S. Trible Jr., who recently announced plans to retire from the Senate next year, former state attorney general and gubernatorial hopeful J. Marshall Coleman and Rep. Stan Parris -- embraced the banner-waving throng as new arrivals to the Republican Party.

"I don't think anyone should apologize for you being here today," Coleman said. "We are not ashamed of you, we are proud of you."

However, most other Republican leaders were far more circumspect about the role of Robertson's forces in next spring's round of party caucuses and mass meetings, the traditional method for selecting national convention delegates and one that the GOP was expected to endorse again on Sunday.

"If the mass meetings were held today, they'd take the whole state," said one senior party strategist, clearly perturbed by the prospect of a Robertson primary victory next year.

"Pat Robertson does not have a majority within the party, but he has built a base outside the party, and a lot of people are going to be real shocked," the official added.

Carol Ann Coryell, a longtime Republican activist in Northern Virginia who is directing the statewide campaign of Republican presidential candidate Jack Kemp, said Robertson will "certainly be a factor" next year even though rivals Vice President George Bush and Sen. Robert Dole (R-Kan.) enjoy far more popularity in the state.

"Robertson supporters are active in our PTAs, we go to church with them, we go to the same grocery stores," Coryell said. "All of the sudden, people in the party are nervous. It's the unknown. It's never happened before."

Eugene A. Delgaudio, a 32-year-old political consultant from Falls Church, traveled by bus with his wife and their three small children to be with Robertson today. Robertson's agenda, he said, "got me motivated, got me out of my chair to be here."

"There are other candidates, but on the three big issues -- the family, right to life and a strong economy -- Robertson's the clear choice," said Delgaudio, a lifelong Republican. Holding a "Fairfax for Pat" sign above his head, he added: "We're here for a fair shot at the presidential nomination. If not us, who? If not now, when?"

The convention participants paid $25 each to register and be eligible to vote in the straw poll, a fund-raising tactic that spokesmen for absent candidates criticized as a "poll tax."

"If the terms were fair, we'd participate," said Marvin Bush, the son of the vice president, who spent the weekend here. "My father's campaign is not about filling up buses and filling up exhibition halls."

Many of those who traveled to this Shenandoah Valley city to socialize and plot election strategy with their GOP brethren said they believed Robertson's chief weakness to be his somewhat narrow appeal to voters nationwide.

"You have to look for electability on a national scale," said Michael Holm, a ranking member of Alexandria's GOP committee. "Your mainstream Republican voter, the Republican activist in this state, is probably going to be for Bush or Dole."

Holm was one of a number of young professionals at Ingleside who said the state party is rebuilding after a series of electoral losses, a job made all the harder by a relative shortage of Republican officeholders. "We have absolutely got to win the governor's race next time," Holm said.

Before that race in 1989, however, comes what GOP leaders concede will be a tough contest against former Democratic governor Charles S. Robb for the Senate seat being vacated by Trible. Although there may be no shortage of GOP candidates next year -- three possibilities, retired Army general Jerry R. Curry, U.S. Customs Commissioner William von Raab and well-known party operative Andrew Wahlquist attended the convention luncheon today -- no one is expected quickly to match Robb's extraordinary appeal with voters.

"Chuck Robb is popular, but everybody has vulnerabilities," said William H. Stanhagen of Alexandria, who today announced his intention to retire from the Republican National Committee next year after 16 years.

"He was a baby-sitter governor, and we were asleep at the wheel for not taking him to task on it," Stanhagen added.