WITH VIRGINIA'S Democrats humming in harmony behind Gerald L. Baliles for governor, the pressure was on the Republicans -- and yesterday, Stan Parris took a cue and stepped aside to pave the way for the GOP nomination of Wyatt Durrette. As Rep. Parris noted, "In the words of Kenny Rogers, you have to know when to hold 'em and know when to fold 'em" -- and victory just wasn't in the cards. Maybe some other time, Mr. Parris hastened to add, but for now he is content to stay in Congress and help the GOP state ticket in the fall. So much for high drama at either party convention next month; but the contest itself could be a good one.

At this point, most handicappers would give Mr. Baliles an edge -- based on two bits of history that Mr. Durrette surely will move to address: 1) Mr. Baliles beat Mr. Durrette for state attorney general last time, and 2) the Democratic ticket's sweep in 1981 produced an administration in Richmond that has won generally good ratings over the years. It will be up to Mr. Durrette to demonstrate why he is a better candidate against Mr. Baliles now than in the previous contest -- and why the Democratic control of the state house has been so bad under Gov. Robb that it should be switched to the Republicans.

The first challenge -- shaking a "loser" label -- should be easier than making the case for election; after all, this Baliles-Durrette race is for a different office. Now you're talking top duty in Virginia, not top legal adviser -- and past voter preferences may have no bearing once the two candidates are pressed for their views on a far broader range of policies. Besides, voter attitudes about the same two candidates can change significantly in no time; just ask Mr. Parris or his longtime rival, Herb Harris, about ins, outs and turnarounds.

In Virginia, the toughest part of the contest usually is the jockeying for position. The inside track is actually in the middle of the road, which is where Mr. Baliles overtook Richard J. Davis. Who will master best the Old Dominion political art of moderation, laced with the requisite regard for Northern Virginia and each of the other parts of this vast land of varied interests? Let the parties begin.