Rep. Harold Washington's surprise victory Tuesday in Chicago's Democratic mayoral primary was viewed yesterday as one of the strongest of several recent indications that newly registered black voters turning out in unusually high numbers can be a pivotal political force.

Washington won in a three-way primary in which two strong white candidates essentially split the white vote and Washington received overwhelming support from blacks--including an estimated 200,000 who came on the rolls during the last year in an extraordinary registration drive.

Although blacks have been one of the most loyal voting blocs in the Democratic Party, their concerns often have been given short shrift, some observers said yesterday, in part because black registration and black voter turnout have lagged well behind that of whites. Washington's victory and black gains in Congress, legislatures and city halls across the nation could change that, the observers said.

"If there is a national significance to the outcome of the election , it increases the credibility of the black vote in the minds of those who would seek national office," said Eddie N. Williams, president of the black-oriented Joint Center for Political Studies here. "Hopefully, the black vote will become the apple of the eye of both parties and avoid a situation where one party takes you for granted and the other ignores you altogether."

"It raises the stakes," said Martin D. Franks, executive director of the Democratic Congressional Campaign Committee. "If there's a way that someone has successfully tapped the potential of the black vote and can wield it into a potential bloc, it is a great potential benefit."

There are an estimated 17 million voting-age blacks in the nation. About 60 percent of them reported in the 1980 census that they are registered to vote, according to the National Coalition on Black Voter Participation, an umbrella group of 88 voter registration and voter education groups, most of them black. By comparison, the reported registration of whites was 68 percent.

In 1980, an estimated 51 percent of the blacks who were of voting age took part in the presidential election, compared with 61 percent of whites. However, between 1964 and 1980, the percentage of whites who voted dropped by 10 points, while the percentage of blacks decreased by 7 points.

Gracia Hillman, director of the coalition, said that preliminary reports indicated that as a result of Washington's registration campaign, 75 percent of all voting-age blacks were registered for Tuesday's Chicago primary.

Of that group, 85 percent cast ballots and 80 percent of those who did supported Washington, according to the Rev. Jesse L. Jackson of the Chicago-based Operation PUSH, who worked with the Washington campaign.

"More and more blacks are turning their rage into political potential," Jackson said yesterday. "What you really saw Tuesday was a political riot, disciplined rage."

Williams and other observers attributed a considerable part of Washington's victory to local issues but said a further catalyst for increased registration was a strong feeling that President Reagan's policies--especially those affecting the economy--are having an especially heavy impact on blacks.

Political observers said the new surge of black voting began to surface in 1976, when blacks supported Jimmy Carter overwhelmingly and tipped the election to him.

Last November, voting almost exclusively for Democrats, blacks helped them pick up 26 seats in Congress, increased black House seats from 18 to a record 21, and raised the number of black state legislators by 17 to a record 337, the Joint Center said.

Center officials said blacks also played key roles in Democratic gubernatorial victories in New York, New Jersey and Texas and near-wins in Illinois and California.

Some of the most prominent black political gains have been in major cities. Among black mayors are Tom Bradley of Los Angeles, Coleman A. Young of Detroit, Ernest N. Morial of New Orleans, Andrew J. Young of Atlanta, Kenneth O. Gibson of Newark, Richard G. Hatcher of Gary and Marion Barry of Washington.