By electing Douglas Wilder, a Democrat and a black man, lieutenant governor, Virginia's 85 percent-white electorate not only made history last week, it delivered a crushing setback to the Blame-the-Customer school of political analysis. This is the school that always explains the defeat of its party's nominee by blaming it not on the shortcoming of the candidate but on the blood lust, dumbness, meanness, racism and/or sexism of the voters. As an explanation for political defeat, it has always been convenient and generally wrong.

Just how wrong was proved by the brilliantly unconventional campaign that Doug Wilder ran. It began with a bold premise, a premise not shared by a lot of white liberals or by most white conservatives: that white voters will vote for a qualified intelligent experienced candidate who happens to be black. And that was precisely how Wilder ran, emphasizing his credentials rather than the color of his skin but never making an attempt to conceal his race. Last Tuesday Wilder won nearly twice as big a percentage of Virginia's white vote as the Democratic ticket of Mondale and Ferraro won one year earlier. Three out of four Virginians who voted for Doug Wilder were white.

To manage his campaign, Wilder made a characteristically unconventional choice: a white lawyer and native of Florida, Paul Goldman, 37, who had spent many years working for causes and candidates that sought to afflict the comfortable and to comfort the afflicted. Goldman, who had lived a year in a Chicago public housing project as a VISTA volunteer, was not the kind of selection designed to "reassure" the Richmond establishment. But while he had "supporters who felt Paul was confrontational and even antagonistic," Wilder explained, "I trusted him implicitly, admired his passionate commitment and wanted his brilliant mind."

Together they developed and implemented a campaign plan that astutely robbed Virginia voters who might have been so inclined of all the easy rationalizations about why a black ought not to get their vote.

To de-demonize his candidacy for rural voters and to put the lie to racial bigotry about anybody's aptitude for hard work, Wilder, between Aug. 1 and Oct. 3, drove some 3,718 miles while personally campaiging in 340 Virginia cities and towns and all of its counties. Along the way, as Wilder was "retailing" and recruiting individual voters in barbershops and grocery stores, Goldman helped devise the "wholesale" strategy that became the campaign's TV commercials.

Those commercials made it more difficult not to vote for the Democrat. Included among them were a strong endorsement by the immensely popular Gov. Chuck Robb and a testimonial from a uniformed Virginia police officer (looking and sounding like central casting's small-town southern sheriff) who announced that he and the Fraternal Order of Police were supporting Wilder.

As the candidate explained the strategy, "our objective was to persuade voters to ask themselves 'why not?' rather than 'why?'

But the boldest decision of all was the campaign's most crucial strategic move to ignore the anxious advice of many of Wilder's most loyal and savvy supporters and to put Doug Wilder on TV prominently in his own commercials. Virginia knew that the 1985 Democratic candidate for lieutenant governor was black.

More important than how the campaign was won is what it could mean for the future of our politics. First, the winning candidate: "You have to speak for more than a narrow constituency. You have to reach out. You have to be broad-based, and you can't be provincial." To Goldman, the manager, the win proves that "Americans, just like Virginians, will respond if we appeal to the best in each other."

After the tensions of 1984, there is an appropriate irony in the fact that the historic election of 1985 was the work of two friends, a black candidate whose grandparents were slaves (in the same city where he will be inaugurated) and a young Jewish lawyer who, in the era of government for the overdog has long been a battler for the underdog. And let us remember the most important element of all: the 45 percent of white Virginia voters who proved that the smart money was wrong, that whites will vote for a good candidate who happens to be black.