I have looked at some historical data from the American Conservative Union. Lately I've heard and read countless pundits attempting to apologize for McCain by pointing to his lifetime ACU rating of 82.3 which almost all of them say is "not bad." Now that's not exactly a ringing endorsement as it is but let's look a little deeper.
I pulled his ratings from every year he has been in the Senate from 1987 through 2006 (the last year for which data is available). While his lifetime average may be 82.3 it is interesting to look at his ratings over time.
McCain is unarguably an incorrigible hothead; known for holding grudges. When he lost the Presidential nomination to W. in 2000, he began to punish W. and the Republican party. As a result, his ACU average from 2001 to 2006 is only 73. This places him below every Republican Senator except Ted Stevens (AK - 64.5), Susan Collins (ME - 55), Olympia Snowe (ME - 49.9), and Arlen Specter (PA - 44.7), unless you count Jim Jeffords and Lincoln Chafee as Republicans.
This is not the best company to keep.