The modern version of: "Let he who is without sin cast the first stone" has arrived. It is: "Let he (or she) who has not told his accountant to do whatever they can in order to pay the least taxes cast the first stone."
Tom Daschle's resignation should have been accepted, however, that of Nancy Killefer should have been refused. Responses must be tailored to the "sin." Not all imperfections make a person unfit for office.
Like many decent people, Daschle got caught in a bad system that is so corrupted by money it hardly matters whether the money is from good people with good intentions or bad people with bad intentions.
The only thing more implausible than believing that a multi-millionaire with national ambitions would willfully try to defraud the IRS of $140,000 is believing that a man like that actually does his own taxes.