Massachusetts Gov. Michael S. Dukakis yesterday named Harvard Law School professor Susan Estrich to be the new campaign manager of his drive for the Democratic presidential nomination.

The 34-year-old Estrich is one of the younger "old-timers" of the Democratic political wars, having worked in the presidential campaign of Sen. Edward M. Kennedy (D-Mass.) in 1980 and the Mondale-Ferraro campaign in the fall of 1984. In the spring of 1984 she was executive director of the Democrats' platform committee, which produced a document supporting traditional Democratic initiatives on domestic issues, but also called for strengthening national defense.

Estrich will take the chair vacated by Dukakis' close friend John Sasso, who quit the campaign last week after admitting that he had provided reporters damaging information about one of Dukakis' erstwhile competitors, Sen. Joseph R. Biden Jr. (D-Del.).

Dukakis has not yet filled the post of political director on his campaign staff. That job had been held by Paul Tulley, but he, too, quit the Dukakis campaign because of fallout from the Biden incident.

The departure of Sasso and Tulley cost the Dukakis campaign the services of two highly experienced political strategists with broad contacts among rank-and-file Democrats coast-to-coast. Estrich's expertise, in contrast, has been more in the area of substantive policy concerns than in political maneuvering.

Sasso had been Dukakis' most trusted adviser for almost eight years. Because of the Biden incident, though, Dukakis has pledged that Sasso will have no further role in his campaign, official or unofficial. "I intend to abide by that guidance," Estrich said yesterday.

Estrich said her policy experience was fitting for the Dukakis effort because the governor is running "a strong, issue-oriented campaign."

The burning question surrounding Dukakis' campaign now is how badly he has been hurt among loyal Democrats because of his campaign's contribution to the downfall of Biden, which occurred while Biden was chairing the Senate Judiciary Committee leading the fight against the Supreme Court nomination of Judge Robert H. Bork.

Preliminary soundings among political pros suggest that the Biden business was not particularly damaging for Dukakis in New Hampshire, where the Massachusetts governor is a known commodity. But it may have fallout among the Democrats of Iowa, where Dukakis is less well known.