7pm This episode's headline: Campaign '88; Walter Mondale; David Brinkley. The guests include In Minneapolis/St. Paul: WALTER MONDALE, Former Vice President; In New York: DAVID GERGEN, U.S. News & World Report; EARL CALDWELL, New York Daily News; In Washington: DAVID BRINKLEY, Journalist; In Chicago: MARK SHIELDS, Washington Post; REPORTS FROM NEWSHOUR CORRESPONDENTS: TRIONA HOLDEN, BBC. Byline: In New York: ROBERT MACNEIL, Executive Editor; In Washington: JIM LEHRER, Associate Editor