As it is, requests for public comment - the feedback to them goes straight into the paper shredder, but if you throw a bit of money towards the re-election fund, you can write the legislature.
It's corruption, pure and simple.
Consider a U.S. Senator representing Arkansas considering a bill regulating nuclear energy. The Senator is no expert in nukes. How should he determine to whom to speak? If a renowned nuclear physicist in California wants to speak with the Senator, should that be banned?
Lobbying, i.e. people--individually or in assembly--expressing their political views to elected leaders, is an inherent side effect of the First Amendment. (And, I'd argue, of democracy.)
The process can be corrupted, but that is true regardless of the vehicle.
Two factors over which we don't have a national consensus.
One: the line between political and non-political speech is tough to draw. If I write a blog about the minimum wage, is that political? What if I do it full time? Now I hire a copy editor--is that political spending? What if the blog is openly--and intentionally--partisan?
Two: a metric to determine the degree to which money is a factor in a given piece of speech. Say I paint a political mural on my house's public-facing wall. Is the paint political spending? What if I hire someone to paint it for me, but based on my design? What if my neighbor lets me paint her house? What if my other neighbor, to whom I give the oranges from my orange tree every year, lets me do the same? What if I commission the art but paint it myself?