I disagree totally. Most Americans want something substantive done on the border, that includes independents and reasonable democrats. What Bush suggested today is more than he's suggested before, and if it's all done, it would make a significant difference. The democrats are on the losing end of this since they will oppose it, and by proxy, be opposing border security, and that will cost them at the ballot box.
Bush needs Democratic votes - lots of them - in both chambers, to get this thing passed. I don't know what calculations you are making.
My guess is that democrats are not going support Amnesty untill after the election. Then they will go full tilt for it. They are evil that way.