Donald Trump derided former Defense Secretary Robert Gates, calling the national security official a "clown" and a "mess." The attacks came after Gates expressed concern about Trump's readiness to be commander-in-chief. Gates, who served under both Republican and Democratic presidents, wrote that both Trump and Hillary Clinton "have a credibility problem in foreign affairs" before singling out the Republican nominee as "in a league of his own" and "beyond repair" on security issues. "We had a clown today, an absolute clown, Robert Gates," Trump told a crowd. "He's supposed to be an expert. He's been there forever ... he goes out and he says negative things about me. I never met him. I never talked to him. Believe me, I am so much better at what he's doing than he is."