68 Percent

Ben Ginsberg writes at Politico:

The 2012 presidential election was the first time the new rules took effect, and they dramatically prolonged the primary season. In every election since 1996, the GOP had settled on a clear nominee in March—as early as March 4, in McCain’s case. Although Mitt Romney did as well as any of his predecessors early on in the 2012 primary—effectively tying Iowa, winning New Hampshire, losing South Carolina, and then winning Florida and Nevada—he didn’t have enough delegates to secure the nomination until April 24, after 41 states had voted. Critics blamed Romney’s long slog on weakness as a candidate, but the changes in the primary calendar certainly played a major role.

The 2016 rules are much the same as the ones that dragged out Romney’s victory, but the circumstances of the race all point to a longer, harder fight. Traditionally, the Republican nominee is known when more than 68 percent of the delegates have been chosen, which won’t happen until April 19 this year. On top of that, the race itself is far more complex than it was in 2012: Romney’s anti-establishment challengers petered out relatively quickly, while the two candidates currently leading the polls this year—Donald Trump and Ted Cruz—are themselves anti-establishment candidates, and are continuing to gain momentum just as the voting season begins.
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June 7: The Final 303
5 states; 303 delegates chosen, 100 percent of the total cumulatively

History suggests that these final five states will be anti-climatic. But if the outcome remains unsettled, the survivors will have to navigate California’s massive 172-delegate haul, which awards three for each of the 53 congressional districts, with only 13 for the statewide winner. Like Bush’s Florida and Kasich’s Ohio, Christie’s New Jersey is a true statewide primary, awarding its winner all 51 delegates.

At this point, the remaining candidates will also need to step up their efforts to win over the Republican version of super-delegates—the 168 members of the Republican National Committee, three each from the 56 states and territories. They are the convention’s only guaranteed delegates. While some states bind their RNC members to vote for their statewide winner, no delegates are bound to a candidate for votes on the convention rules, credentials and platform committees. Since RNC members tend to disproportionally end up on these committees, look for the candidates to court them.