Centrist third party's path to 270

[Former President tack50]

Well, first you would need 2 very bad and extremist candidates from the major parties, as well as that centrist independent being at least somewhat populist.

Looking at the third party vote in 2016 and just extrapolating, the hypothetical map would probably look something like this:

Centrist independent: 280
Republican: 155
Democrat: 96