Just hours after returning from a trip across Asia, Mr. Trump left Washington on Friday for a Halloween party and a fund-raiser at his Florida residence. When he weighed in briefly on the shutdown, it was to cast the potential loss of benefits that millions of Americans rely on for groceries as mostly a problem for Democratic voters. Rather than offer steps he might take to bring the crisis to a close, Mr. Trump called attention to the new details of his renovation of a White House bathroom.