“Do away with Senate elections and you do away with party bloc control of the Senators.”
If Senators are chosen by the state legislature as provided for the in the original Constitution, in any state where one political party controls both houses of the legislature, the Senator chosen will be a member of that party. Currently 32 state legislatures are controlled by the Republican party. Democrats control 13 states and those legislatures will certainly elect a Democrat. The remaining states have divided government so the process required to elect someone suitable to both party would likely be messy in this polarized era.
Selection of Senators by legislatures won’t completely eliminate party block control of the process, but as you pointed out it will tie the process to local corruption, not national. Hopefully it will also make the voters more discerning in the selection of their representatives in the legislature. Certainly it will result in more money from outside the state being employed in local elections as well as more outside political activists being used in local campaigns. More litigation, funded by outside interests, is also likely. Outside organizations will challenge redistricting by the legislature and will also sue over voter registration laws and practices.
The effect would be to dilute the opposition. In the Senate, there are 33 concurrent races; in the House, there are 435. That would be a lot of activism to spread around, and in a very visible way.
-PJ