From The New York Times:
[John McCain] is in the midst of an at-times awkward transition — from being one of the most disruptive figures in his party to someone playing it safer, not to mention trying to make nice with Republicans he clearly despises and who feel similarly about him.
…snip…
One of the trademarks of Mr. McCain’s rebel image has been his inability to cloak his emotions, especially anger. He has been prone to volcanic blowups over the years.