Horse Trading

I'll put this as simply as I can: there's absolutely nothing wrong with Senators voting for a bill if and only if a provision they support is added to the bill.  There's nothing wrong with bill sponsors, or Senate leadership, adding provisions to a bill in order to secure the votes of various Senators.  There's also, for what it's worth, nothing wrong for a Senator to agree to vote for something in exchange for commitments to bring something else to the floor later (or not bring something else to the floor later). 

That's textbook legislating.  It's not a corruption of the normal process; it is the normal process.

To be sure, it's totally legitimate to complain about any item in a bill.  If you happen to be Senator Tom Coburn, you probably think that most government spending is a corruption of the proper role of the federal government.  Fair enough, if you so believe.  But that's a substance, not a process, criticism. 

The whole reason the Constitution and the system that has evolved from it empowers individual legislators is so that they can look out for parochial needs of the folks back home.  That's a feature, not a bug.  And certainly not corrupt.