Complex sentence: Should there be a 2009 United States Senate special election in Illinois to replace Obama and a member of the Illinois Congressional delegation to the 111th United States Congress be victorious, this would also necessitate a special election in that person's district for a replacement.
Split into simpler sentences: Should there be a 2009 United States Senate special election in Illinois to replace Obama and a member of the Illinois Congressional delegation to the 111th United States Congress be victorious. This would also necessitate a special election in that person's district for a replacement.