David R. Gergen, who worked as speech writer or press spokesman for presidents Nixon, Ford and Reagan, has been named editor of U.S. News & World Report, according to Mortimer B. Zuckerman, editor in chief of the magazine.

The 43-year-old Gergen, who left the White House in 1984 as communications director to become a columnist and fellow at the American Enterprise Institute, fills the position vacated in January by Shelby Coffey III, who resigned after nine months to be editor of the Dallas Times Herald.

Gergen, who joined U.S. News as a contributing columnist in January 1985 and became a managing editor in August, became senior managing editors and de facto editor after Coffey's departure.

"As we have worked closely together over the last two months, it has become easy to conclude that David Gergen has the leadership ability, news judgment and personal vision to become a great editor of U.S. News," Zuckerman said in a statement.

The appointment of Gergen, whose expertise has been primarily in politics rather than journalism, came after numerous staff members lobbied Zuckerman to allow Gergen to replace Coffey, according to several staff members.

At the same time, Zuckerman reportedly was negotiating with other possible replacements for Coffey outside the magazine. Last week, Osborn Elliott, dean of Columbia University's Graduate School of Journalism, said he turned down Zuckerman's offer of the editorship after he became concerned that Zuckerman would command too much editorial control as editor in chief.

In his statement, Zuckerman said he and Gergen "worked out the details over the last month, making it possible to proceed with this announcement today."

"I was delighted that so many staff members came to me, all with the same conclusion -- that Dave should become the new editor," Zuckerman said.

Gergen said in the statement, "It was the vision of U.S. News as a great newsweekly, one that could blaze fresh trails of insight and interpretation, that originally drew me to the magazine. As I have learned over the past year about the strength and inspiration of Mort Zuckerman and members of the staff, I am more convinced than ever that we will succeed."

Gergen, who is a graduate of Yale and of Harvard Law School, worked as a speech writer and researcher for President Nixon and was director of communications for President Ford. He was communications director for President Reagan from 1981 through early 1984.

Asked whether his strong ties to the Republican Party over the years might present problems for him now as an editor, Gergen said yesterday that he had spent the past two years trying to gain a position of independence from the Reagan administration.

"One of the most encouraging aspects of this appointment has been the support from within the staff, working with me day to day . . . I feel comfortable in the role," he said. "Mort also feels that this is not a problem. As far as I can tell, it was not even an issue in the consideration on his part."

At the magazine, insiders suggested that moving from politics to journalism is increasingly accepted among members of the news media. Diane Sawyer of CBS once worked for President Nixon. President Johnson's press secretary Bill Moyers later became editor of Newsday. Jody Powell, President Carter's press secretary, writes a column.