Why would Klobuchar call O'Rourke too extreme? He's actually to her right on some issues (notably trade and healthcare), and where he is to her left it's nowhere near far enough for her of all people to launch an independent campaign against him. I mean we're talking about a woman who signed on to the Green New Deal here...
For this reason I don't think Amy's campaign gains much traction at all and she barely outperforms Jill Stein or maybe Ralph Nader if I'm being generous. This makes the election an easy curbstomp for Beto, as the much greater split would be in the GOP between Cruz and Pence. If Beto won the nomination, he must have been popular enough that there is no way Democrats are gonna turn on him for Klobuchar who would just be seen as a sore loser. Bernie doing that instead makes much more sense, especially if he only lost narrowly as you say. It would also make for a much more interesting map probably. But as it is...
O'Rourke 462Cruz 42Pence 24Klobuchar 10And that's being pretty generous to Amy. If her impact was even lower, she wouldn't win her home state and O'Rourke could win nearly every state.
Honestly, the scenario you described reminds me more of both 1912 (GOP fatally split, Dems win big) and 1980 (Moderate challenges his party's nominee for being "too extreme," barely makes a dent).
