First, Sanders lost Nevada because Hillary Clinton won the caucus.
Then, the Sanders campaign put their ground game into effect, in an effort to overtake Clinton during the nearly-unique-to-Nevada process that allows for changes in pledged delegates at later caucuses. But he didn’t get enough delegates to achieve that. The Sanders campaign does get credit for getting more delegates than they had before, of course.
Then, at the State Convention, Sanders had enough delegates in place to gain a couple of more delegates and possibly tie with Clinton in the end. But the organizers for the Sanders campaign failed to ensure that all the delegates to that convention were totally on board with what they needed to do in order to be credentialed at the event. Of the thousands of delegates at the convention, a handful of Clinton delegates failed to be credentialed (an expected number) but something over 60, initially, of the Sanders delegates were not legit, so they could not participate. A few of those managed to get credentialed by clarifying their information, but most did not. I’m not 100% certain of this, but I think that had they all been credentialed there would have been enough Sanders delegates to win one more delegate.
The fourth failure is complex, and mainly philosophical. First, Sanders supporters around the country are complaining a lot about how the Democratic Party process is an insiders game and ignored the will of the people. This is odd, considering that the will of the people leans strongly towards Clinton. In any event, the Sanders campaign playing the ground game in the middle of the Nevada process was inside politics. This sort of inside politics is perfectly normal, legal, expected, and what you have to do if you want to win. But by complaining loudly about the Clinton campaign doing this sort of thing, and then doing this, Sanders lost a moral high ground. The fact that this particular moral high ground does not exist to begin with means that this is merely an annoyance, but it is annoying.
Another part of the fourth failure is the cacophony of Sanders voices complaining about getting screwed in Las Vegas (I’m sure they weren’t the only ones that evening). This is a problem because it engenders bad feelings among democrats, but the accusation is based on nothing. What really happened is that the Sanders campaign tried to grab a couple of more delegates, but owing, I think, to too many people involved being ignorant of how the system works, failing to do as well as they might have. This same ignorance has led to unfounded complaints about what happened at the Nevada convention. This whole thing, this fourth way of losing, has given people whoa are getting tired of the Sanders followers more of a reason to call for Sanders to drop out of a race he has already lost. That loss may be more important than the small number of delegates that the Nevada Sanders campaign organizers failed to get.
A few points for those not fully aware. First, the numbers of delegates at the convention is very large, and the number of delegates who were not credentialed is very small, a fraction of a percent. Second, yes, this convention was chaotic, but guess what: they are all, always, chaotic. What happened at this convention was mostly pretty normal, though the Sanders antics did make the event run way more over time than usual. Another thing that was a bit unusual was that they were allowed to go over time by three hours. That is fairly remarkable. Usually, a extended event (caucus or campaign) shuts down much sooner.
Both campaigns had people involved in counting delegates, credentialing delegates, and running the meeting. This was not a case of Sanders people all on the floor and Clinton people running the show. Rather, both Clinton and Sanders people were involved in all aspects of this convention, and both Sanders and Clinton people, for the most part, acted properly during the event. I think it was just a small number of Sanders people who were causing all the extra raucous, and later complaining about it.
When considering the events in Nevada, remember that no two caucuse systems are alike, and the Nevada system is probably much less like the others than any. People are calling for a revision of the Nevada system, to not allow so much changing around of delegate pledges after the initial causus (though that has nothing to do with what happened Saturday), but actually, this system is better for the campaign process and for democracy. First, candidates have to demonstrate that they are willing to do more than just show up for a few days of stumping and buy a few ads. They have to be involved at the state and local level the whole time. Second, if there is a shift in the opinion of party mebmers as to who should get the state’s delegates, this allows for that adjustment. In this case, the adjustment mainly indicated a shift towards Clinton and away from Sanders. Thus, the Sanders people are a bit upset. Understandable, but just part of the process.
By and large, a lot of Democrats (both Sanders and Clinton supporters) are deciding to love or hate a the process, or a particular part of the process, based on whether their candidate won or lost. Please stop. In fact, estopp. You signed up for the game, this is the game, these are the rules. Feel free to suggest changes in the rules, but you can’t issue a complaint when the rules are followed but you didn’t get your way.