Maybe you came across this. How did they deal with split legislatures prior to the 17th?
I don’t know. If you mean, the state house votes one guy, the state senate another, I think it was only up to the house. If you mean a divided house where no one got the vote, I think the seat stayed open until someone was appointed.
The US Senate explains its own history:
http://www.senate.gov/artandhistory/history/common/briefing/Direct_Election_Senators.htm