Republican National Chairman Frank J. Fahrenkopf Jr. warned his party's governors today that GOP hopes in 1986 may be blighted if Democrats follow the lead of Virginia Gov. Charles S. Robb and the successful Democratic campaign in the Old Dominion this year.

While agreeing with pollsters and political consultants who told the 13 GOP governors meeting here that their party is well-positioned to end its minority status in the states, Fahrenkopf said Robb and the Virginia example could short-circuit that dream.

He said that the 1985 Virginia ticket, guided by Robb, was allowed to "race unfettered to the center and throw the Republican Party off to the extreme right."

Fahrenkopf warned that Robb, who leaves office next month, and Democratic National Chairman Paul G. Kirk Jr. have been talking recently "as if they were long-lost brothers," and the recent Virginia campaign may be the model that "Democrats everywhere use against us in 1986."

He said Democratic Gov.-elect Gerald Baliles, Lt. Gov.-elect L. Douglas Wilder and Attorney General-elect Mary Sue Terry were "three liberals" who "out-Republicaned the Republicans" by emphasizing fiscal responsibility and a tough stance on crime and drugs.

Fahrenkopf declared that similar candidacies could succeed in other states unless Republicans "find the right fulcrum to throw the Democratic Party off-center."

His words, at the opening session of a two-day meeting of the Republican Governors Association, threw a dash of cold-water realism on the generally upbeat tone of the meeting.

The association chairman, Pennsylvania Gov. Richard L. Thornburgh (R), said that the GOP "can score a net gain of eight to ten governorships" in 1986, when Democrats must defend 27 of the 36 gubernatorial offices at stake.

Republicans currently are in control of only 16 out of a total of 50 governorships.

Fahrenkopf and GOP pollsters Robert Teeter and Vincent Breglio cited studies showing that President Reagan's high approval ratings have carried the GOP to a position of "near-parity" with the Democrats.

"For the first time in my 20 years of work," Teeter said, "we can use the name Republican" advantageously to identify GOP candidates in most states. "I've worked for nothing but nonpartisan candidates until now," Teeter quipped.

The pollsters and political consultants said that if Republicans break the normal pattern of severe reverses for the party in power in the sixth year of a presidency, then it might be safe to talk about political realignment.

But New Jersey Gov. Thomas H. Kean (R), whose landslide reelection victory last month was cited as a model by almost every speaker, said he worried about what would happen to Republicans "when we lose Reagan as a candidate and the inevitable [economic] downturn comes."

The main emphasis of the day was on showcasing initiatives Republican governors have taken in recent years to develop innovative programs in education, economic development, the environment and social programs. Slick brochures outlining 86 such programs are designed as campaign handbooks for other GOP gubernatorial candidates, who will have a $1 million national campaign fund available to them, Thornburgh said.

Tennessee Gov. Lamar Alexander (R), who initiated the effort to catalogue these programs, said that as Washington officials, preoccupied by deficits, "focus exclusively on war, welfare, Social Security and debt," governors must become "activists" supplying "strategic thinking" for their states. "Sticks in the mud will not be elected on either ticket," he said.

J. Hugh Nichols, the executive of Howard County, Md., who switched parties earlier this year and is expected to seek the Republican nomination for governor, participated in the panel on "new ideas."

Nichols told the GOP governors that, under his prodding, the Chamber of Commerce and the United Way had stepped forward in Howard County to replace human-service programs cut by the Reagan administration. He also said the business community had raised $750,000 to build a sewage-treatment plant that allowed development to go on when federal financing was delayed.