re. campaign finance laws and the notion that money is "speech"

A campaign donation is not an argument; it's a simple statement of support.  A larger donation does not add anything to the content of this statement.  It is both literally and metaphorically a matter of volume, nothing more.

Therefore, a limit on the amount of a donation does not constitute a limit on freedom of expression; it merely places restrictions on how a simple assertion may be expressed in the public sphere.

Nobody considers it unreasonable that we have laws against shouting through a megaphone at 3 AM in a residential neighborhood.  And yet, how much more obnoxious and disruptive to the harmony of our society is excessive campaign spending?