I see that Gary Johnson is going to be invited to the next debate, this one in Florida on Thursday. Good for him, I suppose.
It occurs to me as part of my position that there's no particular reason for debate sponsors to be "fair" to candidates -- what they should be is responsive to party actors and fair, if you call it that, to party actors and party voters -- that the current use of polling to determine who is invited is pretty much a bad idea, but one that we're stuck with for understandable, even good, reasons.
What should happen is that the political parties choose who gets to be invited to the debates, using any criteria they believe is appropriate. But there's a paradox involved, because the nomination process is in part all about choosing who gets to make party decisions -- so at this point, no one really has the uncontested authority to do so. That's presumably a piece of any party nomination process, but it's especially problematic for American political parties because the formal party structure isn't necessarily central to what "the party" actually is. Nor are there formal party members, who could then elect party officials and give them some legitimacy. Instead, there's an odd situation in which formal parties set some of the ground rules, but are otherwise often unimportant to party governance, all of which makes whatever they do contested when candidates believe they have been wronged. Which also means that those formal party officials themselves are on precarious ground. All of this, of course, applies not just to relatively trivial stuff such as whether Gary Johnson gets to debate, but also to things such as the timing and rules of the various primaries and caucuses. The debates are relatively easy; turn it over to the network sponsor and hope no one makes a fuss. The schedule of primaries and caucuses is a lot harder.
At any rate...it's clearly unfair to Johnson as a fairly recent former governor that he hasn't been included in the last four of these things, but there's no reason for the party to be fair to Johnson or the rest of them.