The quirks of the GOP primary system are getting their closest attention since Gerald Ford and Ronald Reagan battled all the way to the convention in 1976—including a loophole that the New York Times believes could cost Donald Trump the nomination. Pennsylvania has 71 delegates, the most of any remaining state save California, but only 17 of them will have their first-round convention ballot choice determined by the primary vote. That leaves 54 delegates, three from each congressional district, to be selected by GOP primary voters—but the delegates are free to vote for the candidate of their choosing at the convention, and the primary ballot won't indicate which candidate they're likely to support.
By the Times' calculations, Trump would probably win at least 40 Pennsylvania delegates under another system, but the quirk could cost him just enough to fall short of the necessary 1,237 delegates at the convention. The Pittsburgh Tribune-Review notes that in 1976, the Pennsylvania loophole was a factor so important that Ronald Reagan named Pennsylvania Sen. Dick Schweiker as his running mate long before the convention—only to lose the nomination when powerful delegation chief Drew Lewis had the entire delegation back Ford. NBC News reports that aides to Ted Cruz, who's around 20 points behind Trump in Pennsylvania polls, have been pushing a slate of Cruz-loyal delegates and expect to get around 30 delegates from the state, even if he finishes third in the voting. (His new slogan is "Yes We Will.")