7PM This episode's headline: Agonizing Decision. The guests include SEN. ARLEN SPECTER, [R] Pennyslania; SEN. ALBERT GORE, [D] Tennessee; MARK SHIELDS, Washington Post; DAVID GERGEN, U.S. News & World Report; LEE CULLUM, Dallas Times-Herald; GERALD WARREN, San Diego Union; CYNTHIA TUCKER, Atlanta Constitution; ED BAUMEISTER, Trenton [N.J.] Times; PATRICK McGUIGAN, Daily Oklahoman; ERWIN KNOLL, The Progressive; CORRESPONDENT: ROGER MUDD. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER