I am sure that he thought the left would continue to support him.
The minute he became the leader of the Rs, he became the enemy.
Police: McCain volunteer changes ATM attack story
http://www.breitbart.com/article.php?id=D94106P03&show_article=1
Hmmm, perhaps KDKA was correct.
I'm sure you're right, and his failure to anticipate this is a serious defect. My perception is that he believes that his long history of accommodating the Democrats (aka betraying his own party, though I'm sure he's never seen it that way) has made them his friends. He can't have failed to notice the unrelenting savagery of their attacks on W for eight years, but apparently he interpreted that only as disagreement with W's policies.
If he's beginning to understand the reality of Democrat hatred (as indicated by his campaign's increasingly tough ads), his still-ongoing attempts to appease them indicate he's a long way from understanding it fully.