That is an interesting concept I've never heard before.
I think it would be worthwhile to research:
1) Why the original Constitution had state Senators elected from the legislatures instead of a direct vote of the people. I've always thought it was because the state legislature was a republican-type representation of the people of the state more than a direct vote which is simply a flat democratic majority-rule that can drown out the votes of the smaller communities. I like that idea, of course, but not sure it has made that much of a difference in that aspect of things.
2) What was the reason and intent of the ratifiers of the 17A for going to a direct popular vote.
if the Senator were to run a campaign appeal to the people that was disconnected from the interests of the state legislatures
Seems like you've got a root problem if the wishes of the people of the state are disconnected from their own legislatures.
It's not that the people are disconnected, it's that they don't pay attention. That's why we have a representative government, so that we can pick people whose job it is to pay attention. Then we grade them on their performance when they come up for re-election.
-PJ
You should read the scholarly papers by Todd Zywicki in this thread, Repealing the Seventeenth Amendment, especially this one. It lays out the common reasons why the 17th passed, and then tries to disprove them by pointing out incongruities in the arguments, and then finally explains a market within the Senate for trading political votes based on longevity (the ability to back up the promise of future votes due to the guarantee of being there).
The bottom line (to me, anyway) is that the original system wasn't corrupt enough, which is why the 17th was passed -- to give Senators (as power brokers) the ability to promise to deliver legislation because of the guarantee of remaining in the Senate long enough to make good on trades for votes.
-PJ