Biden on Alito and one-man one-vote

I was just listening to Fox News Sunday where Chris Wallace was interviewing Senator Joe Biden. Biden was outraged: "The part that jeopardizes it (Alito's nomination) more is his quotes in there saying that he had strong disagreement with the Warren Court particularly on reapportionment - one man, one vote." This is going to be some what amusing to see US Senators go after Alito on this given that Senators are elected to represent such differently sized states. The original Supreme Court decision dealt with the issue of state Senates, but it was never clear to me what US Senators could represent different size constituencies, but state Senators could not.