What Obama should say about McCain's climate promises

Obama should continue to tie McCain to Bush, saying something like this:

George Bush, like John McCain today, promised in 2000 to regulate carbon dioxide emissions and to require all power plants to meet clean-air standards in order to reduce carbon dioxide. Two months after he was elected, he broke his promise and fought environmental efforts ever since. On this issue, like so many others, we cannot afford a third Bush-McCain administration.

This puts McCain into a tight spot of dealing with Bush's broken promise. The best he can do is to plaintively say he won't break promises like Bush did, which won't be very convincing to environmental voters and won't exactly energize Republican voters either.