WITH VIRGINIA'S election recipe for instant lame-duck governor every four years, there is always an element of the unknown once the winning candidate thanks his supporters and prepares to take over. Will he make good on anything promised during his run for the office? And what about those quiet little pledges made to certain groups that then delivered critical turnouts around the state? Gov.- elect Charles Robb has wasted no time paying his respects to supporters, and in a post-election interview with Donald P. Baker of this newspaper, has made an important commitment to minorities and women--who helped make the difference this year for the Democratic ticket.

Noting that he is "committed to acting affirmatively," Mr. Robb says there is no question that women and blacks will have a greater voice in the management of the state when he takes office on Jan. 16 as the first Democrat in the governor's mansion in 12 years. The governor-elect stressed that he will "look beyond the traditional sources" from which state officials have been selected in the past in an effort to convince blacks in Virginia that if they are well-qualified, there is a role for them in state government.

Certainly there should be, but it has been fairly well camouflaged in the past. Four years ago, in his inaugural address, Gov. John N. Dalton made a similar pledge; but hardly anyone would argue that there have been noticeable differences in the complexion of the state government since. That is not a matter of Mr. Dalton's good faith being in question, because after all, he owed no special favors to minorities.

But in this election, the difference was apparent immediately. Mr. Robb won overwhelming support from the state's black and women voters--and they have good reason to expect consideration for jobs throughout the government. In his first six months, Mr. Robb will have about 2,300 jobs to fill, and the positions involve all echelons of government, which allows for more than merely high-visibility appointments at the cabinet level.

There are other encouraging words for Northern Virginia in Mr. Robb's announced agenda. Not only is he committing himself to support for the full 101- mile Metro rail system but he plans to review the alignment of the controversial Springfield Bypass.

Delivery is the real test, of course, but on this score, Mr. Robb will enjoy several advantages. The lieutenant governor, attorney general and the majorities of both houses in the legislature all are members of his party. And Mr. Robb has asked Lt. Gov.-elect Richard J. Davis, whose knowledge of govermnment at all levels is impressive, to act as the governor's chief of staff.

According to Mr. Robb, Virginia can look forward to more than "a caretaker governor" come January. That isn't likely to mean revolution, because Virginia has never been known for violent political shifts. Still, Gov.-elect Robb's determination to make government more representative and to recognize the importance of northern Virginia bodes well for a more progressive government in Richmond.