There is, as far as I can tell, no positive evidence that Mr. Bush is a man of exceptional uprightness. When has he even accepted responsibility for something that went wrong? On the other hand, there is plenty of evidence that he is willing to cut corners when it's to his personal advantage. His business career was full of questionable deals, and whatever the full truth about his National Guard service, it was certainly not glorious.
I love Krugman's comment about the missing photo of Bush swimming the Yangtze River (Mao's old standard). Twenty-seven Bush photos in the Federal budget .... that's a cult of personality, reminescent of Reagan.
I don't think Bush is evil, but he's as dishonest as any President and a better liar than most. He also has been venerated (literally) by the evangelical right; they believe he has been anointed and appointed by God. To challenge Bush's integrity is to challenge either their understanding of God or to challenge God Himself.
It will be a very nasty campaign.