There is a serious risk of actual bias when a person with a personal stake in a particular case had a significantand disproportionate influence in placing the judge on the case byraising funds or directing the judge’s election campaign when thecase was pending or imminent. The proper inquiry centers on the contribution’s relative size in comparison to the total amount con-tributed to the campaign, the total amount spent in the election, and the apparent effect of the contribution on the outcome.
They then find that the contributions in this case had a "significant and disproportionate" effect on the outcome of the case, and that the judge in the case should have recused himself. Of course this is a pretty squishy standard, a fact that Chief Justice Roberts makes clear in the dissent where he lists forty different questions (via Vince) about how the standard should be implemented. It's clear though that the real divide is between those justices who are opposed in general to campaign finance limitations, and those who are not, with Justice Kennedy (in this case but not in others) siding with the majority. I think this case is an excellent example of the dangers of our present system of campaign finance (generally private) but as you can see, the circumstances must be fairly extreme (one-sided contributions in a judicial campaign where the contributor is before the judge) before the Supreme Court is going to reach out to the Constitution to permit limitations on financing. I applaud the fact that five out of nine of the justices think that there's a point at which it's just too much, but this is a pretty backhanded way of getting at campaign finance reform. Impartiality in judges is hardly a guarantee whatever manner in which they are placed on the bench, but this case should be a lesson to states that appointments, or at least state funded elections, are by far the most reliable way to avoid the appearance of (or actual) bias on the bench.