For years, the White House saw House Majority Leader Eric Cantor as a chief driver of Republicans' staunch opposition to nearly all of President Barack Obama's agenda. Now, Cantor's stunning primary loss seems likely to make politics even more difficult for Obama. Rather than opening a pathway for the president, Cantor's defeat could push Republicans more to the right and harden the House GOP's hostility toward the White House, virtually dooming Obama's efforts to pass a legacy-building immigration bill or other major legislation....