I think 1960 & 2008 were some nails in the coffin of the "Qualified Person should get the job" approach.
I say 1960 changed the game because it was when televised Presidential Debates became a thing. Not just in the USA but around the world, when we could actually SEE the candidates' animated face and their mannerisms, we weighted aesthetic characteristics more heavily than before. (You can see this all around the world. World leaders are becoming younger and younger and more handsome or gorgeous. They're becoming younger and stronger even in the last eight years. If you stand Obama 'circa 08 next to Singh or Marcon, Obama '08 is nearly a decade older and less physically in shape.)
'08 was a game-change as well because: two mavericks defeated the party consensus, the top three candidates (Clinton, Omaha, McCain) were standing senators, and all were wildly under-qualified for the position. Anyone who says that Omaha won for any reason besides his charisma, is a liar1. Similarly, anyone who says that Trump won for any reason besides his braggadocious nature and charisma, is deluded1. The USA may never give a monotone, crippled man the presidency again. I doubt Canada will vote for a party who's leader has Bell's Palsy again.
1 Some would say it was Omaha's/Trump's policy positions that propelled them to victory. Considering how many positions they flipped on so casually over the years, I am skeptical of that being a primary contributor to their successes. In other words, I think Barrack Rand or Donald The Marxist would have done comparably well as the personae who ran.