The Senate’s top Democrat said Thursday his party is prepared to block the nomination of Neil Gorsuch to the Supreme Court by filibuster. The pledge by Minority Leader Chuck Schumer sets up a confrontation with Senate Republicans, who have threatened to invoke the so-called nuclear option to push through Gorsuch’s confirmation. The move would change Senate rules to allow confirmation with a bare majority of senators, rather than the 60 now needed to overcome delaying tactics.