NO. 2 REPUBLICAN IN SENATE CALLS FOR VOTE ON LOTT
Sen Don Nickles, second-ranking Republican in Senate, is first Republican senator to call for his colleagues to consider replacing Trent Lott as majority leader; no other Republican senator goes as far as Nickles, but several do agree that they must meet quickly to confront controversy that has engulfed Lott; some say there should be reevaluation of whether he sould serve as Senate's Republican leader; Nickles, who has long had designs on Lott's job, says he is concerned that Lott has been weakened enough to jeopardize his ability to enact Republican agenda; says he accepts Lott's apology for remarks he made at Sen Strom Thurmond's 100th-birthday party that have touched off examination not only of his record on civil rights but also of party's history on subject; controversy that has engulfed Lott has not subsided despite his numerous apologies; photos (M)