Virginia Lt. Gov. L. Douglas Wilder challenged members of the Harvard Black Law Students Association tonight to become "involved in the political and economic day-to-day operations of our country."

Wilder, whose election in November made him the nation's highest elected black state official, said, "People who say politics is a dirty word" want others to believe it so the vital decisions of government "can be left entirely to them."

His speech at the Copley Place Marriott marked the start of a nationwide speaking tour put off until last week's closing of the Virginia General Assembly. Wilder hopes to show Democrats, particularly black Democrats, that they can win despite seemingly long odds.

During those visits, he said he will look for possible recipients of aid from his Underdog Fund, which he announced shortly after his January swearing in. Wilder said two "underdog" candidates his fund may aid are Dwight Evans and Reavis Goff, blacks seeking Democratic nominations for lieutenant governor in Pennsylvania and Colorado, respectively.

Kenneth Lewis, a third-year law student from Winston-Salem, N.C., said Wilder was asked to be the main speaker at the weekend conference "because we recognize him as the top black elected official at the state level" in the country.

Wilder told the audience, which included most of the 160 blacks who make up about one-tenth of the enrollment at Harvard Law, that when he graduated from "that other law school that ends in RD -- Howard," in 1959, an average of one black passed the bar exam in Virginia each year.

"I decided if one would pass, I would be that one, and true to form, only one passed and I was that one," he said.

Wilder said he mentioned that "not to brag" but to remind today's minority students that "you could never have had the opportunity to matriculate here" if others had not "fought assiduously" to open up the great institutions.

There is nothing wrong with looking forward to becoming a partner in a law firm and joining a country club, he said, but there is a continuing need to "give back . . . benefit those who have not had" the opportunity and education they have had.

Before his speech tonight, Wilder met privately with Massachusetts Gov. Michael Dukakis, who Wilder said encouraged him to travel and spread the word of the Democratic sweep in Virginia. "He thinks we took some issues, such as crime, away from the Republicans," Wilder said of Dukakis.

Wilder, who spoke to a meeting of regional directors of the NAACP in Washington Friday, will be back in Washington next Saturday to receive an award from the National Bar Association.

Then he will go to Taiwan to represent Virginia at a trade fair. In the following weeks, Wilder said, he has speaking engagements from coast to coast.