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Donald Trump keeps breaking his ceiling because of a little thing called the “bandwagon effect.”

The states along the Northeast Corridor that voted Tuesday should have been prime Kasich territory. Republicans there are more moderate and less religious than they are in the heartland and the South. Kasich even grew up in McKees Rocks, Pennsylvania. All of that should have smoothed the path for his brand of “hug your neighbor” conservatism. Instead, Trump won all five states in play tonight.

Those results were in line with what political scientists call the bandwagon effect: Voters tend to support whoever is leading in the polls. With only 82 days left before the Republican convention, Trump’s momentum is only accelerating. At this point, he could very well win the nomination outright before the convention. That possibility, the bandwagon theory suggests, will only serve to drive more voters his way.

Kasich and Cruz keep telling voters that Trump can’t beat Hillary Clinton in the general election. “You have only one choice,” says the narrator in a recent campaign ad for Kasich. “One choice that will stop the Clinton political machine: John Kasich.” Cruz told his supporters on Tuesday night, “Donald Trump is the one man on earth Hillary can beat in a general election.”

But as Jeff Greenfield pointed out in Politico this morning, “Electability isn’t the message that galvanizes a party base.” Polls matter more. And in that respect, Trump has a yuge advantage.