[dragonwriter]

> Clinton locked out nearly all of the viable opponents by using institutional control, the only one left was one sufficiently outside the Democratic party so she had a strong institutional advantage. No voting system could have fixed that.

Uh, yeah, simply not having voting superdelegates in the nominating contest (a reform to the candidate-selection voting system Democrats made in response to 2016) would have likely fixed (or at least mitigated) that, since the nominating contest was close even with the early superdelegate commitments and the effect that had on the perception of inevitability.

A general election direct (no electoral college) voting system like Bucklin or IRV, modified some that the same ballots, skipping votes for the winner, were tallied again by the same method to select the vice president, encouraging a party to bring it's two independently strongest candidates into the general election (and increasing the space for other parties or independent candidates) would absolutely both discourage that and limit the effect it would have on constraining viable general election choices.

(The same system internally to the party for choosing the Presidential and Vice Presidential nominees also would fix it.)

[yyyk]

The superdelegates went for Clinton because there wasn't any serious institutional D challenger (Sanders was an independent before), so Clinton had by default a huge advantage there. If there was a serious internal D challenger, the picture would have been far more equal.

IRV can make the contest more fair than the previous voting system, but it can't make candidates run...

[dragonwriter]

> The superdelegates went for Clinton because there wasn't any serious institutional D challenger

No, that's s almost exactly backwards. A key way Clinton locked out other traditional candidates was to secure an unusually large number of superdelegate commitments extremely early, needle other candidates would normally commit to the race.

> IRV can make the contest more fair than the previous voting system, but it can't make candidates run...

Yes, it can. Running in a Presidential primary (and the same is true of many other races) is an investment of time and resources people make—or avoid—in part because of the perceived prospects for success factors like a competitor having a substantial share of the total available vote sewed up before you decide, or a voting system that naturally narrows the field people will actively consider during the campaign do, very much, effect who decides to run.