WASHINGTON — Assemblyman Jay Webber, seeking the Republican nomination to replace retiring Rep. Rodney Frelinghuysen, picked up the endorsement Tuesday of a potential rival, who decided not to run himself. Webber, R-Morris, received the backing of Assemblyman Anthony Bucco, R-Morris, who also was considering entering the race to succeed Frelinghuysen, R-11th Dist., but chose not to.…