From this Rolling Stone Article

At least three of McCain's GOP colleagues have gone on record to say that they consider him temperamentally unsuited to be commander in chief. Smith, the former senator from New Hampshire, has said that McCain's "temper would place this country at risk in international affairs, and the world perhaps in danger. In my mind, it should disqualify him." Sen. Domenici of New Mexico has said he doesn't "want this guy anywhere near a trigger." And Sen. Thad Cochran of Mississippi weighed in that "the thought of his being president sends a cold chill down my spine. He is erratic. He is hotheaded."