The Extreme Court has no respect for the Constitution.
The court would probably find such an action unconstitutional.
I would enjoy seeing some well informed speculation from Free Republic commenters about which current or historical politicians would - or would not - have become Senators under the current election rules, or, by vote of a state Legislature.
For instance - Lincoln lost the 1858 Senate election by vote of the Illinois state Legislature. It is quite possible Lincoln would have won a popular election in Illinois.
For instance - I think Ted Cruz would have had a very difficult time being elected by the Texas Legislature