Dump Trump? Very hard to do. But there's precedent for replacing a nominee.

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Is there any precedent for all of this?

There is. Richard Winger, the editor of Ballot Access News, points out that in 1912, the Republican incumbent nominee for vice president, James Sherman, died in October. His name remained on the ballots but all of the Republican electors voted for the new vice-presidential nominee, Nicholas Murray Butler, who had been chosen in late October by the national Republican committee.

On the Democratic side, the death of Horace Greeley in 1872 came after the election but before the Electoral College cast its votes.

In that case, most electors voted for other presidential and vice-presidential candidates.

Congress rejected the votes by Democratic electors that went to Mr. Greeley, who had lost to Ulysses S. Grant.

“The electors are the deciders,” Mr. Winger said. “I suspect there are a few Republican electors who expect to be elected and who are planning to vote for someone other than Trump. I think both Evan McMullin and Gary Johnson are trying to persuade various likely Republican electors to vote against Trump in the Electoral College in December.”