Senator Russ Feingold to the Supreme Court?

Here's an idea:  Senator Russ Feingold to the Supreme Court when Justice Souter steps down.  He is a graduate from Harvard Law School (same class as Roberts, '79), a former attorney, and most importantly, a staunch, principled defender of the Constitution.  Since Republican Senators know him as a colleague (and he is, by all accounts, widely respected), they will have a hard time voting against him during the confirmation process.  What an asset he would be on the court: a politician who can think.