It’s unlikely, but far from impossible
The idea that an independent candidate could swoop in to win has been largely dismissed, on the grounds that any conservative-leaning third-party candidate would be more likely to hurt Trump than Clinton, thus making a Clinton victory more likely. But McMullin may have one advantage that other second-tier candidates do not: Utah.
His path to the presidency basically looks like this:
1.Win Utah
2.Deadlock the Electoral College
3.Win in the House
Read it all [h/t AS Haley]
Ala John Quincy Adams; and we all know what a successful presidency he had.