I've never heard a Senator admit to constant campaigning, but I haven't heard everything you have; regardless, anyone serving a six year term and making that claim is indulging in rhetoric. Senators have a broader and larger constituency (usually; obviously that doesn't apply in places like WY) that tends to require they pay their political dues before a successful run. It's not uncommon for a wealthy private citizen to get incensed over a single issue, make a few speeches and end up in the House, but that's much less common in the Senate. The nature of their constituency makes them a little more deliberate, a little more measured, and that's usually reflected in their debates. It's less so than it used to be because those and the additional qualities the framers endowed the Senate with motivated them to make the Senate the primary executive oversight, and that has resulted in a higher level of scrutiny that encourages extremism as partisanship grows.

But having state legislatures select Senators is in the same vein as restricting the franchise to free male property owners over 21, IMHO. Though, having said that, I do support 21 being the universal age of consent, be it for booze or ballots. We need a cutoff that's necessarily arbitrary, but I think it should be uniform, and the higher we set it the less people will be legally engaged in practices for which they lack the maturity. Twenty-one is high enough to be beneficial but low enough to be fair, again, IMHO.