But Justice O'Connor's position is that the public purpose must be to remedy an affirmative public harm, and not merely to substitute some more desirable benefit.
The real problem here is the incorporation of the Constitution. The Founding Fathers never envisioned the Constitution applied to this scenario in any way at all, and so they didn't phrase it accordingly.
Being broke and having crummy schools, and having crowded roads, and air pollution, are all public harms. It is a distinction without a difference.