The specific actions the DNC took to cause Bernie to lose includes: 1) They chose to put the debate between Hillary and Bernie at MIDNIGHT so people wouldn't watch the debates. It was at the start of the primaries when people didn't know much about Bernie so the DNC decided that nobody watching the Democrat's primary debates helped Hillary

2) In the debates, they gave the questions to Hillary before the debates. The DNC controlled debates gave them to a CNN person who would give them to Hillary

3) The DNC owns the decision about Super delegates. Super delegates == ignoring one-citizen-one-vote

4) Arizona greatly reduced polling stations. With 3+ hour waits, people gave up. The DNC knew that Hillary voters voted at a higher ratio on mail-in-ballots, so it skewed to Hillary.

5) The California level had Bernie votes made in a way that they were all not counted:

In California 2016 election, "NPP" (Non-party voters) the election committee training pole workers to give them "provisional ballots". All of those NPP votes ("provisional ballots") were thrown away. The only NPP voters that could be counted were "Democratic cross-over ballots", but they they poll voters weren't trained that way. Bernie Sanders votes where thrown away. In California Bernie had 61% in polls against Clinton, but then lost. . https://www.youtube.com/watch?v=MoGeDGHmwJU

This article is making it's rounds. It implies that Hillary had control of the DNC and "bailed it out": https://www.politico.com/magazine/story/2017/11/02/clinton-b...

They advertised her superdelegate lead before the voting even began. They leaked debate questions to her in advance of the event. They smeared Bernie with unfair accusations and labels. They worked directly with big media outlets to either deny or put out negative coverage of Bernie. The Washington Post put out 16 negative stories on Bernie in one day. There was unregistering of progressives in New York, and a botched delegate counting process in Nevada. They reduced the number of debates before the first primary by at least a third. DNC leads got caught actively cheating, leading to their resignations - Debbie Wasserman Shultz and Donna Brazile. They actually used the excuse in court that the Democratic party is private and has no legal obligation to run fair elections, and could select in a backroom smoking cigars if they wished. They actually said on national television that superdelegates served the purpose of preventing grassroots candidates from winning. I could go on and on. All of these things are easily verified. I can give you more if you'd like, with references.

I don't think you can point at a specific action, but the leaked (Podesta, I think) emails seemed to show that the DNC was working to help the Clinton campaign to the detriment of Sanders during the primary. This lead to the resignation of Debbie Wasserman Schultz from the DNC chairman position.

Later, it turned out the Clinton campaign had essentially taken over the DNC far in advance of the primary results which is highly unusual, to the say the least. [1]

[1] https://www.politico.com/magazine/story/2017/11/02/clinton-b...

Hillary won like every southern state, the Bernie folks are living in fantasy land if they think the DNC could control that outcome.