Sound like a conflict of interest? Under current Court rulings, it's not. The judge had nothing riding on the outcome of the case. But the fact that he was willing to hear a case involving such a prominent supporter suggests a conflict.
If the Court finds that it did represent a "probability of bias," the decision will have implication in all the states that elect judges, where multimillion dollar campaigns have become common and judges haven't been too good about recusing themselves from cases involving their benefactors.
Separately, the Washington Post reports today on a Virginia group looking to impose term limits on judges and make the selection process more open to the public. Virginia is one of two states, along with South Carolina, where judges are selected by the legislature.