Hillary Clinton and Donald J. Trump have drawn closer to their parties’ nominations with almost every passing week. The five elections on Tuesday — in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island — may offer them their best chance before June to gain a final, decisive advantage over their opponents.
But Senator Bernie Sanders of Vermont has been a tenacious opponent on the Democratic side, and could find precincts of strength even on a Primary Day that favors Mrs. Clinton. Gov. John Kasich of Ohio and Senator Ted Cruz of Texas face even more daunting terrain on the Republican side; for them, this week is a battle for survival.