A WHITE SOUTHERNER, Charles (Chuck) Morgan Jr., ruined what could have been a thriving legal practice in Birmingham, Ala., in the early 1960s by defending civil rights demonstrators and blaming the white establishment for the atmosphere of violence that led to racially motivated bombings and killings.

Later Morgan represented Capt. Howard Levy, a doctor who refused to train Green Berets to be medics, and Cassius Clay before he became Muhammad Ali. He also was one of the first to attack the legality of the Vietnam War and to call for Richard Nixon's impeachment.

Always an iconoclast, Morgan broke with conventional liberalism in 1976 when he supported a fellow Southerner, Jimmy Carter, for the presidency -- a move that drew so much criticism that he was forced to quit the American Civil Liberties Union after 12 years as a staff attorney in Atlanta and here.

Now Morgan has formed his own eight-lawyer firm, Charles Morgan Jr. & Associates, defending corporations from what he considers assaults on their constitutional rights.

This new activity has drawn cries of "sell-out" from some liberals -- cries that intensified last week when Morgan filed, on behalf of Sears Roebuck and Co., a legal assault on federal affirmative action employment efforts. The suit charges that government policies over the past five decades created the present "unbalanced workplace" dominated by white males that private industry is now directed to end.

The suit flies in the face of present liberal ideas of encouraging affirmative action programs to bring more minorities and women into high-paying jobs.

Conventional wisdom in legal circles here holds that Sears can't win. Aware of that view, Morgan replied, "That's what they told me when I filed Reynolds vs. Sims," one of the companion cases with Baker vs. Carr that led to the Supreme Court's one-man, one-vote ruling and changed the face of American politics.

Morgan is no stranger to unpopular causes, although he has usually been on the side of the left.

Yet at the time he was attacking racial segregation in the South he appealed on constitutional grounds contempt of court convictions against some of the most vocal supporters of moves to defy court desegregation orders. They, too, deserve to have their constitutional rights defended, Morgan said at the time.

So do businesses, Morgan said recently.

His firm represents the Tobacco Institute in its battles against no-smoking laws. The firm also filed a suit on behalf of the Grocery Manufacturers of America, charging Carol Tucker Foreman, a former consumer advocate who is now assistant secretary of Agriculture for food and consumer affairs, with conflict of interest in issuing regulations. That suit was dismissed.

Morgan said he sees little difference in being paid by the Tobacco Institute to represent a woman in Newport News, Va., who doesn't want to ban smoking in her coffee shop and in taking the cases of blacks fighting segregationist policies of the Birmingham city government in the 1960s.