Today fifty Republican Party national security experts published an open letter declaring they will not vote for Trump, saying he “would put at risk our country’s national security and well-being.”

This is unprecedented.  These are the guys who have been very unhappy with Obama, and by default Clinton, yet they find their own party's nominee far worse.  This is not a "liberal attack" on Trump.  These are some of the most conservative and highly informed individuals in the country saying this man is an existential threat to America.  

http://www.nytimes.com/2016/08/09/us/politics/national-security-gop-donald-trump.html?smid=tw-nytpolitics&smtyp=cur