"I think his mind is visceral," [Gary] Hart said, "driven less by thought and more by feelings. This doesn't mean he's totally reactive or without logic or thought processes; it just means he's a fighter pilot. He reacts to circumstances."
A senior official in the Clinton administration who worked with McCain on Bosnia and Kosovo, where McCain defied most of his Republican colleagues to support strong U.S. action against Serbia, agreed. "In the many, many years that I've been in Washington," this former official said, insisting on anonymity to avoid upsetting McCain, "John McCain is far and away the most emotional politician I have ever met."
"McCain is all emotion," the former official continued. "People don't understand that, so they keep talking about his temperament, his temper. He reacts emotionally, therefore unpredictably."
McCain's demonstrable lack of a guiding political philosophy over the years makes this a pretty credible analysis.