*sigh*
New congressman was from SD. Had an
Arterio-Venous Malformation, or AVM, not a heart attack. Had brain surgery for it.
He has not been replaced, since the only way to replace a sitting congressman is in case of death or resignation. The republican governor can indeed name a replacement, but only in those circumstances, neither of which is imminent.
Presuming a republican governor would appoint a republican congressman (now far afield in your hypothetical case), the balance of power in the Senate would shift to 50 republicans, 49 Democrats and 1 independent, and of course, the president of the Senate is Dick Cheney, the Vice President, a republican. So, potentially the balance of power would be 51-50 in favor of the republicans.
Did that answer your question?