Who will be the first candidate to announce and when?

[ꙮ]

Trump, within a year of the current date. Nobody else will join the primary for a long time after that. You’ll get a couple other challengers: a never-Trumper (Hogan or Kasich), perhaps someone from the “Libertarian wing” (Sasse or Massie), and maybe you get a more mainline Trumpish Republican who says the party needs someone new and younger (Haley?).

I don’t see there being much of a primary. It will be like an incumbent renomination more than an actual primary process.