For an early debate, I think one of the main goals would be to give exposure to "deserving" candidates who don't necessarily already have it. Polling isn't good for that since it will exclude anyone people haven't already heard of. But the question becomes what is "deserving" and how do you measure it?
It's not like counting donors is perfect, but what is? And it has some things going for it:
1. Talk is just talk. If you can get a decent number of people who don't personally know you to support you with at least a few bucks, you've got some kind of appeal.
2. There are already a lot of laws, reporting rules, etc. around campaign donations that you can piggyback off of. That is, the campaigns are already tracking this stuff very carefully and, if they cheat the numbers, are risking something a lot worse than being left out of a debate.
You can also qualify by getting 1%+ support in 3+ "approved" polls.
You'd be surprised
Meeting either criteria qualifies a candidate for the debate, and should the field of qualifying candidates grow to more than twenty (gods forbid) priority is given to candidates that meet both and then by polling average.
A GoFundMe could raise more than that.
As a Democrat, I'm okay with showing a minimum number of individual donors. It shows real interest in the candidate.
As opposed to the DNC clown car from 2016 where everything about the primaries was pre-cooked by DNC insiders and their media helpers?
I don't understand how any rational person can claim moral high ground for either party.
One, maybe two things, ISTR, no?
That was settled well before the primaries were done, so if that's just one thing, it's enough. You don't even need to get to "two things" like previewing questions with the media for the debates, or purging dissenters from the DNC leadership, for example.
The funniest thing I heard on the subject was the suggestion to nominate Trump as a Democrat so he qualifies for their primary debates and can take on all of them at once.