Actually, the rules on the governor replacing a vacancy in the Senate vary from state to state.
For instance, I think it's Arizona where a member of the same party must be appointed. Other states differ.
Calling the SD constitutional expert!!
Seems at though he can appoint whomever he pleases to fill the vacancy wit, regardless of party.
http://legis.state.sd.us/statutes/DisplayStatute.aspx?Statute=12-11-4&Type=Statute
South Dakota Constitution
12-11-4. Temporary appointment by Governor to fill vacancy in United States Senate. Pursuant to the Seventeenth Amendment to the Constitution of the United States of America, the Governor may fill by temporary appointment, until a special election is held pursuant to this chapter, vacancies in the office of senator in the Senate of the United States.
Source: SL 1979, ch 99, § 1.
Seems at though he can appoint whomever he pleases to fill the vacancy with, regardless of party.
http://legis.state.sd.us/statutes/DisplayStatute.aspx?Statute=12-11-4&Type=Statute
South Dakota Constitution
12-11-4. Temporary appointment by Governor to fill vacancy in United States Senate. Pursuant to the Seventeenth Amendment to the Constitution of the United States of America, the Governor may fill by temporary appointment, until a special election is held pursuant to this chapter, vacancies in the office of senator in the Senate of the United States.
Source: SL 1979, ch 99, § 1.
ABC radio new's 1st worry was the balance of the senate possibly going to republicans...