The only way I know is for him to talk directly to the people about it - not with his usual vapid, wishy-washy, platitudinous burbling, but by really articulating the reasons why this law is so dangerous not only to individual liberty, but to the integrity of our political system as well. I know it involves a risk, but what is there that's worthwhile that doesn't involve a risk? He may be able to pick up a few votes for his party here and there, but the country's still going to continue sliding to the left unless someone - especially someone with his visibility and popularity - starts educating people about what it means to have the right form of government.
It'll be easy for the Dems and the McCainiacs to demonize him if he constantly lets them have the mike.
The problem is, again, you have him giving his explanation versus millions of dollars spent in thirty-second attack ads. Have you already forgotten the 1995 budget battle? Even if we're right (as we were back then), if you can't sell it in a twenty-second soundbite, you are screwed.
The long-term game is the judical nominations, and Bush is going to need all the help he can get to have a Senate that will confirm his nominees. Now, are you going to run off over principle, or are you going to help get people who will be able to protect your principles over the long haul? That is the choice.