Overall a pretty clever system, and a good way to solve the problem of choosing who the important candidates are for people to see, without bias or too much public perception that it's rigged in favor of or against particular candidates because of their views. But I think they made a huge mistake with the rule about polls!
Especially in the beginning, this summer when the debates began, lots of potential voters were undecided and most of them were considering most of the candidates. Even after the first few debates, there were still a lot of undecided voters, and most voters who did have a favorite were still considering others. The point of rules like this should be to show you the candidates you may still be considering, not the candidates you or someone else have already chosen. With these rules, it was quite possible for a candidate who nearly everyone was still seriously considering to be exluded from the debates, while someone else (such as Tulsi Gabbard) who very few people were considering, and who most voters had already decided against, would still be included.
What the DNC should have done is announced in advance that they would *only* consider polls that ask who you're seriously considering voting for. They could've set much higher thresholds, starting with 10% rather than 1%. Debates would then have emphasized showing us all the candidates people actually want to learn more about.
There weren't very many polls like that, but you can bet that if the DNC had announced a rule like that in late spring, there would have been plenty more. And the DNC could have commissioned a few national polls themselves to add to the mix.
Crossposted from Dreamwidth - link to original post ( comments on DW)