NEW YORK—Markie Post, who played the public defender in the 1980s sitcom “Night Court” and was a regular presence on television for four decades, has died. She was 70. Post’s manager, Ellen Lubin Sanitsky, said Post died Saturday in Los Angeles after a years-long battle with cancer. Post was a longtime television regular who appeared in shows from “Cheers” to “Scrubs.” But she was best known for her seven-season run on NBC’s “Night Court,” the Manhattan municipal court sitcom that ran from 1984 to 1992 and starred Harry Anderson as Judge Harry T. Stone. Post became a full-time cast member of “Night Court” in season three as Christine Sullivan, a sincere and strong-willed woman who served as a constant foil to Dan Fielding, John Larroquette’s narcissistic prosecutor. With comic rebuttal, Post’s Christine deflected Fielding’s lechery throughout the series’ run. Though an unrealized romance between Christine and Harry was often teased, …