I remember Trump's first speech in his campaign. No one was sure if Trump was serious about running for president. Trump had toyed with the idea for decades. Then he gave a stump speech. He stood on a soapbox and addressed the widespread outrage about illegal immigration. For our entire national history, we had laws and procedures about immigration, but then came the huge wave of illegal immigrants who trampled on those laws and who expressed their disrespect for their neighbor to the North even though they were clawing to enter the United States for obvious reasons. On the day following Trump's first speech, most of the mainstream news outlets, whether they were print, broadcast, or internet, accused Trump of calling Mexicans rapists. I heard the speech first hand, and I have acquired a transcript of the speech. Trump never said such a thing.
The mainstream media is a corrupt cabal who lied then and who has lied habitually ever since.
Soon a history professor from the University of Texas wrote an op-ed in Salon magazine about the atrocity of the mainstream media altering Trump's words to mean that all Mexicans were rapists. The UT professor was not a Trump supporter. He was a self-avowed Sanders supporter, but he was outraged by the scurrilous and dishonest press. He said that he heard the speech first hand, and though he thought there were some awkward comments that would be used against Trump, he acknowledged that Trump never said such a thing. He expressed his alarm that the press had come to this.
It only got worse in the following months.
Then we discovered that powerful elements in the DOJ launched a coup against the President. We learned that not only was the press a crooked organization who defied their own long-established ethics, but the Obama administration was a criminal enterprise.
The progressives are utterly nihilistic and violent and determined to grip the American public in some kind of governmental authoritarian onslaught that will diminish freedom of speech and other rights. We fought World War II over the threat to such freedoms, and we should fight the "progressives" for the same reason. They are evil and they rejoice in it.
After this Senator Sanders knew he could not get the electoral vote count he'd need so decided to join Biden and give them to him. More to Bernie's fine character. 
