Virginia state Sen. L. Douglas Wilder today backed out of his threatened independent campaign for the U.S. Senate, saying he had succcessfully brokered a decisive new role for blacks in the Democratic Party.

Wilder told a news conference he no longer intended to lead blacks out of the Democratic Party, which has barely a month to pick its Senate nominee. He said in the process of forcing state Del. Owen B. Pickett out the race he had won assurances from Gov. Charles S. Robb and other party officals that black issues will now be at the top of the party's agenda.

"I am certain that our causes will no longer be pooh-poohed and ignored the way they were before," said Wilder, 51, the state's top black elected officeholder.

Wilder, a Richmond lawyer, said today he would not rule out a bid for the Democratic nomination but made it clear he will not be a serious contender in what is expected to be a mad scramble for delegates to the party's June convention in Roanoke.

At least four potential candidates have emerged as contenders for the nomination which, until mid-Tuesday, had been virtually guaranteed to Pickett. They are Lt. Gov. Richard J. Davis of Portsmouth, former state attorney general Andrew P. Miller of Alexandria, state Senate Majority Leader Hunter B. Andrews of Hampton, and Commonwealth's Attorney Robert F. Horan of Fairfax County. None today moved to take advantage of the void left by Wilder and Pickett.

Wilder said he could support either Davis or Andrews but suggested that Miller would be unacceptable. He declined comment on Horan or others, saying he wants to confer with other black leaders before making any endorsement.

W. Roy Smith, a leading figure in the state's powerful conservative business establishment, charged today that Wilder had obtained veto power over the Democratic nominee. As a result, Smith warned that independent, conservative voters may now desert the fragile coalition that last year elected Robb as the state's first Democratic governor in 16 years. Such move could help the expected Republican nominee, Rep. Paul S. Trible Jr. of Newport News.

Blacks turned out in record numbers in that election and played a decisive role in helping to elect Robb, giving him 96.4 percent of their 200,000 votes. Robb won by a margin of l00,960, a point that was not ignored by Wilder either today or in his earlier opposition to Pickett.

There were, however, also some signs of black disenchantment with Wilder's announcement today. Wilder himself acknowledged that many of his supporters who had urged him to run were disappointed with his decision. Sa'ad el-Amin, a Richmond black activist and longtime Wilder critic, accused him of "selling out" by abandoning his candidacy.

To many politicians, Wilder's dramatic announcement -- coupled with Pickett's withdrawal 24 hours earlier -- signaled what many political observers called a historic moment in the evolution of black political power in Virginia.

"I believe what has happened is a victory for blacks," said the Rev. Curtis Harris of the state's chapter of the Southern Christian Leadership Conference. "Had Sen. Wilder not withdrawn, the Democratic party would have been unable to come up with any candidate at the convention."

J. Harvie Wilkinson, a Virginia historian and professor at the University of Virginia, said Wilder had loosened the grip of the state's conservative tradition. "It is the first time ever in Virginia's 20th century history that a prominent black official has altered the entire course of one Virginia's major parties," said Wilkinson.

Wilder turned the spotlight on the racial attitudes of Virginia's political leaders, several of whom were ensnared in a series of politically embarrassing incidents. Two weeks ago, House Speaker A.L. Philpott was forced to apologize for referring to the state's four black delegates as "boys."

And last week, Del. Alson Smith (D-Winchester),a top party fund-raiser and chairman of the House Democratic Caucus, had to admit his reluctance to bringing Wilder into the inner sanctum of the Commonwealth Club, an all-white male bastion of the state's establishment.

Under pressure from Wilder, Robb responded with a series of pronouncements on race issues unheard of in the state since days of liberal Republican Gov. Linwood Holton, who walked his children to an integrated school in 1969.

For example, Robb chose the Wakefield Shad Planking, a traditional political gathering of followers of the old Byrd organization in Southside Virginia, to warn of a the "long, hot summer" that might result from prolonged unemployment among black youth.

After the legislature failed to pass a Wilder bill denying tax exemptions to segregated schools, Robb last month signed an emergency executive order accomplishing the same goal. And in a speech this past Sunday, the governor told a predominantly black audience, including Wilder, that he deplored "the persistence of old attitudes" of some Virginians on race.

Wilder today heaped upon Robb, applauding the governor's unswerving commitment to eradicate the "archaic attitudes of the past."

It was unclear yesterday what precise commitments Wilder had won from either Robb or the legislative leadership. Wilder first threatened to run for the U.S. Senate after two of his bills -- one creating a state holiday for Martin Luther King and the bill banning the tax breaks for segregated schools -- were killed in House committees.

Today, Wilder said he expected changes in committee assignments and other actions addressing black complaints at the legislature's session next year, but he was unable to specify exactly those what those changes would be.

Wilder's tactics may have produced a backlash among some of the state's conservative political figures, many of whom feel they have as legitimate a claim on the Robb administration as blacks do. Smith, who was chairman of the Virginians for Robb, said he was "extremely disappointed to see . . . the party's leadership acquiesce" to Wilder's demands.

Smith, whose endorsement has carefully courted by both Pickett and Trible, warned that conservative voters -- particularly those influential Independents who followed Sen. Byrd and former governor Mills E. Godwin out of the Democratic Party in the last decade -- would be watching carefully for any concessions made to Wilder. "The price exacted by Wilder to earn his blessing will be a factor of major importance in their decision," Smith said.

Wilder made clear he expects his role at the Roanoke convention to be played out behind the scenes. Asked about the possibility of a draft-Wilder movement, the legislator quipped: "I won't be waiting by the window."