The race for governor of Virginia narrowed today into what is expected to be one of the longest, most expensive and, one analyst suggested, most intellectual campaigns in the state's history.

The collapse of Rep. Stan Parris' campaign for the GOP gubernatorial nomination clears the way for Wyatt B. Durrette to begin his battle against Democratic state Attorney General Gerald L. Baliles a month before either party's nominating convention.

"It's going to be a classic battle . . . . " said Ed DeBolt, Durrette's chief consultant in the contest that will pit two moderate-to-conservative candidates in campaigns that could cost a total $6 million and prove crucial to each party's future in the state.

"It's going to be a much more intelligent campaign than we usually have," said Larry J. Sabato, a University of Virginia political scientist who has studied elections in the state for more than 10 years.

Despite their similarities, Sabato said both Baliles, 45, and Durrette, 47, are more likely to focus on issues and organizational campaigns because neither has a "barn burner" style and both lack the "star quality" of Democratic Gov. Charles S. Robb, who cannot succeed himself under Virginia law.

"Ideologically, while they will hype their differences, it's difficult to put a dime between them," Sabato said.

Baliles, who narrowly defeated Durrette for state attorney general in 1981, was assured the Democratic gubernatorial nomination Friday after his only rival, Democratic Lt. Gov. Richard J. Davis, conceded.

"We put some pressure on the Republicans by getting our house in order first," said David Doak, chief strategist for Baliles. "I think it's going to be a spirited and hard-fought battle" for the Nov. 4 general election.

Virginia is one of only two states -- New Jersey is the other -- to hold gubernatorial elections this year.

With Parris out of the race, the Baliles campaign said it expects the Northern Virginia area to be a crucial swing area in the race against Durrette, a former state legislator from Fairfax County who moved to Richmond after his 1981 loss.

Baliles strategists said Parris, as an incumbent member of Congress, had posed more of a problem in the area than Durrette in the battle for campaign contributions and votes.

The attorney general is a longtime resident and former Richmond legislator, and has a hometown following that could undercut what is usually a strong Republican area in state elections.

DeBolt said that the Republicans expected to mount their campaign against the entire Democratic ticket, which he said has "all the ingredients of the traditional Democratic coalition."

He was referring to the expected nomination of State Sen. L. Douglas Wilder (D-Richmond), who is unopposed for the Democratic nomination for lieutenant governor, and state Del. Mary Sue Terry (D-Patrick), running unopposed for the party's attorney general nomination.

"No question it's going to be a ticket-versus-ticket race," DeBolt said from his Northern Virginia offices.

Sabato, who with DeBolt gives Baliles a slight edge at the beginning of the campaign, said he believed it is still uncertain what effect Wilder, who is black, and Terry, as a woman, will have on the campaign.

Durrette "will try to present this campaign as a ticket campaign, projecting his as a solidly conservative ticket in contrast to Baliles', which has more of a tinge of liberalism."

Although Durrette's nomination seems certain, there is a spirited five-way fight for the GOP nomination for lieutenant governor, with most politicians saying the race appears to be between former Republican attorney general J. Marshall Coleman of McLean and state Sen. John H. Chichester of Fredericksburg. State Del. William (Buster) O'Brien of Virginia Beach is expected to be the GOP nominee for attorney general.

The contests also are seen as a battle by the Democrats to hold onto their successes of 1981, when they won all top three offices for governor, lieutenant governor and attorney general, a victory that broke a GOP stranglehold on the governor's mansion that had lasted since 1969.