"Today's opinion requires state and federal judges simultaneously to act as political scientists (why did candidate X win the election?), economists (was the financial support disproportionate?), and psychologists (is there likely to be a debt of gratitude?)," - as quoted from The Washington Post
Um. No. Justice Kennedy is more right than Chief Justice John Roberts. If a judge is hearing a case and one of the parties in the case contributed a lot of money to the judge's campaign, the judge's ability to render an impartial verdict in any given case has been compromised.
If there is any problem with Justice Kennedy's decision (and there is a big one) it is that he didn't go far enough. Judges must specifically be prohibited from hearing cases involving a parties that contributed to their campaigns.
Truly comprehensive reform, however, would require state amendments that remove the selection of judges from the electoral process.