What chance would a third-party candidate have?

Likewise Gary Johnson. Johnson will definitely run, and will certainly have at least a small-scale reverse-Bloomberg effect: He’ll peel off a few classically liberal liberals but many more small-government conservatives. He won’t win an electoral vote either — even if, per a few grandiose predictions, he clears 10 percent of the popular vote. But he might hand Hillary the White House.

Then there’s Mitt Romney. Mitt would win electoral votes — six of them, in Utah, where he won 73 percent of the vote in 2012 (his best state), and where Trump won just 14 percent of the primary vote, finishing behind both Cruz and Kasich. Nationwide, he would attract substantially more support than Gary Johnson, inevitably giving Hillary an enormous electoral landslide. Unless –

– Mitt were to run only in Utah. If Hillary wins Virginia, Ohio, or Florida, it’s all over; she has a majority. But if Trump carries all three, Utah’s six electoral votes would be the difference between a Trump majority of 272, and a Trump–Hillary tie of 266 each. (Assuming, as I do, that Colorado will go Hillary.)

When no one has a majority in the Electoral College, the House of Representatives takes over. Each state delegation gets one vote; currently, the Democrats have a majority of members in 15 delegations, 32 are Republican- majority, and the remaining three are tied.