I think that would be an excellent Kerry response to some of Bush's charges of flip flopping, and it works on a couple of levels.
First off, it's true in the cases of authorizing the Iraq war, the Patriot Act, and NCLB. Kerry voted for Iraq to give Bush leverage to force inspections, but Bush just wanted war. Kerry voted for NCLB because he assumed the Republicans would fully fund it's provisions, but they haven't. While the Patriot Act was dubious from the get go, certainly Ashcroft's implementation has been excessive.
While those to the left of Kerry can say he was too naive to have trusted Bush in the first place, that argument isn't available to the Administration or to conservatives as they can't very well call Kerry a fool for trusting Bush!
It works on another level, too, I think. It's kind of cathartic for those who voted for Bush in 2000 but are troubled by him, now. Also, it casts doubt on Bush's claims going forward. Maybe he talks the talk, but in the end, what he says and does bare little relation.
"We Trusted You, and You Failed Us."
What do you think?