On 18 December 2015 there was breach of political data; that is to say, the DNC's database vendor 'somehow' lost the protective firewall meant to shield competitors' data from each other. This had happened once before. It was Bernie Sanders who without any fuss reported it to Wasserman, who decided to do nothing about it.
When there was a second 'breach'. Wasserman, the leader of the DNC, did not call judiciously Bernie to ask about it. Instead she immediately screamed "foul play." She 'leaked' the story to the New York Times and the Washington Post and other major media friends who supported Hillary. They dutifully reported that Sanders, who is admired for his integrity, was involved in highly unethical political behavior. They never bothered to investigate.
Their collective intentions were clear: to take down Bernie Sanders.
The smear technique Wasserman employed (undoubtedly after consulting Hillary) was informed by none other than Karl Rove.
If you recall, Rove was "W'"s campaign manager. And he had a formidable task of handling 'W' who had ducked active duty in Vietnam by using his father's influence to get into the Texas Air National Guard, then he quit flying, and ultimately deserted the Guard altogether. To make matters worse, everyone knew by that time that Bush was a liar--that there were no weapons of mass destruction in Iraq, and that the war itself was an unmitigated disaster.
Bush's opponent was a highly decorated war hero, Senator John Kerry.
Sounds hopeless, doesn't it? Not to Rove.
Rove's website (Karl Rove's Handbook, Daily Kos, 8 Oct 2012) gives 15 tactics that the Republican party routinely uses that have turned filthy politics into the norm. Tactic #2 advises Republicans to attack your opponent's greatest strength. Tactic #5 advises Republicans to lie--the bigger the lie the better.
Kerry's greatest political strength was his heroism under fire, so Rove assembled a motley crew of disgruntled Swift boat losers and sent them in to smear Kerry. They created stories that were later proved to be unfounded; nevertheless the mainstream media used them to smear Kerry.
It worked" "W" was "reelected."