Thanks - my point is actually narrower. It's that if both sides have enough money to saturate the voters with their message, additional money is of low marginal utility. Otherwise we'd have Meg Whitman as our governor in CA. She outspent Jerry Brown by nearly 5x in 2010, and lost by 13 points.
http://www.huffingtonpost.com/2011/02/01/meg-whitman-outspen...