I'm terribly sorry, but given the highly political nature of this question, as well as the fact that many of the studies done on this violate the 20 year rule we have in place, we are going to have to remove this. /r/Ask_Politics and /r/AskSocialScience would be better suited venues for this discussion.

This may be removed, but to offer an alternative theory as to why this would (often) be the case: rather than assume winning is a product of larger campaign funds, both money and votes could be a product of another factor, i.e. popularity.

A good candidate that is able to persuade people to vote for him is also likely to be able to persuade people to donate money to him.

So a candidate that puts up his own money rather than soliciting donations wouldn't necessarily follow this pattern. Romney, for instance, lost to McCain in the '08 Republican primary despite greater resources. Much of his spending came from his own wealth.