Bernie has been saying Hillary is unqualified since June 2015

The bottom line is that if Hillary was qualified Bernie, wouldn't even be running for President. He would be endorsing her as he did Jessie Jackson. He would just stay in his comfort zone in the Senate and continue to advocate for the things he is campaigning on. Running for President is hard work and we can see how hard it is when we follow Bernie's story he is in a few different places every day campaigning and giving speeches. He does a ton of interviews and during this time he had surgery. You don't do this if you think a qualified person is already running. You especially don't do it when you know that your odds of winning are slim to none. But, if you think that running will give you a platform to avert disaster then you do it because you must. Bernie has realized the disasters that Hillary has caused and will continue to cause if she gets the nomination. Starting with she could lose to the GOP. If she manages to win she will continue policies like those that allow wealthy people to not pay taxes. She will continue to let banks do what they did that created the disaster in 2008 that put people out of their homes. She will continue with bombs for bucks wars. She will continue to support bad environmental policies. She will continue to demonize the young and poor people for wanting free stuff. And she will continue to allow people to be content with the status quo even as it kills them.