Rounds would appoint some random Republican. Daschle would run in the special election and win. He only lost last time because of the highly charged '04 national climate.
Daschle is finished pretty much finished in South Dakota. I could see him running and the only reason he would win is because the voters would feel it is right for a Dem to replace a Dem. Otherwise, I highly doubt a majority of people care about him anymore.
I warn people against being so sure that a Republican would be appointed/win the special.
