As Bush heads toward the final months of a presidency mired in troubles at home and abroad, onetime insiders increasingly have turned on people or policies they had supported. Matthew Dowd, Bush's chief reelection strategist, has disavowed him. John R. Bolton, his former U.N. ambassador, has led the charge against key foreign policy decisions. Kenneth Adelman, a close friend of Vice President Cheney, has denounced what he calls the worst administration in modern times.