Bernie is racking up the wins but the party establishment is safe, thanks to Democratic Superdelegates. Unlike mere mortal delegates they aren’t beholden to any candidate.
Mark Plotkin in The Hill calls the Superdelegate arrangement a House of Lords category that makes the Democratic Party undemocratic.
The Republicans, on the other hand, are all House of Commons – no Superdelegates. The only way for their establishment to stop an outsider like Trump is to back Ted Cruz, an outsider they hate a little less.