The Keystone State is the biggest prize of the GOP’s five-state slate Tuesday night. Trump was also projected to win Maryland and Connecticut as polls closed. Rhode Island and Delaware were not immediately called.

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Pennsylvania has 71 delegates. Trump’s win gives him just 17 delegates. The remaining 54 are unbound and free to support any candidate they like at the Republican convention.

But Trump’s big win puts pressure on the state’s unbound delegates to respect the will of Pennsylvania voters in their convention votes.

A number of these unbound delegates have already suggested publicly that they will respect the popular vote and support the statewide winner.

Trump’s win also deals an important psychological blow to his rivals, particularly to John Kasich. The Ohio governor had targeted neighboring Pennsylvania as a state that would be receptive to his messages of bipartisan outreach and compassionate conservatism.

Kasich allies had cause for hope in Pennsylvania as recently as late March when a Franklin & Marshall College poll had Kasich and Trump neck-and-neck in the state.

But more recent polling showed that survey was an outlier and that Kasich drifted well off the pace in the state.

Maryland has 38 delegates up for grabs, while Connecticut has 28.

- Updated at 8:20 p.m.