Kendall, I agree that big money can't necessarily buy a Senate seat, governorship, Presidency, etc.    But it can, and I think often does, when the candidates and their past performance are not well known by the voters.   And even when the mass infusions of cash don't manage to unseat an incumbent or a popular elected official, they can force that candidate or political party to divert their limited funds into campaigns that normally could rely just on ordinary news media, town halls, and routine campaigning.      

Sure, Meg Whitman and Carly Fiorino and Ross Perot may not have been able to buy election either with their own $ or with $ millions from PACs or corporations or billionaires, but they were running against well-known politicians. And Harry Reid fended off the massively-funded "Tea Party" campaign of Sharron Angle, probably because she was such an extremist nut-case that even those who don't like Harry were even more turned off and frightened by the prospect of her becoming a Senator.   Not to mention that Reid - the "devil you know" - holds a powerful position in the Senate from which to serve the state of Nevada, whereas a freshman Senator would not.

But Russ Feingold - one of the most honest and respected Senators in modern times - was defeated by an all-out $$ onslaught by Karl Rove and the Republican Party and the big financial corporations (targeted because he was a fighter for campaign finance reform and for getting the $ out of Congress), and he was defeated largely because he refuses to take PAC money or donations from big corporations.   Marco Rubio's win in Florida was probably largely due to his being able to self-finance a very expensive campaign. Alan Grayson, like Feingold, was the victim of a huge spending campaign by the "undisclosed donors" to "independent ads" and by the Republican Party, specifically targeted to take out the most liberal members of Congress. And David Bloomberg pretty much bought himself the Mayor's office in NYC. Money doesn't necessarily buy every election, but it often does and even more often has profound impacts on those elections.

The Republicans, and their undisclosed allies (e.g. the US Chamber Of Commerce) don't HAVE to spend $ on campaigns in "safe" districts (where, say, the registration is 70% Republican). Same goes for the Democrats in some districts. But since the Republican gerrymandering that was done in 2000, there are far, far fewer "safe" Congressional districts for the Democrats. That in itself could explain why the Democrats may have outspent the Republicans in House races:   they HAD to, since the 2000 redistricting gave Republicans a big advantage in terms of "safe" districts.

I don't know that the aggregate figures tell a very important story.   Where the big-money campaigns can have the biggest and most devastating effect is in:
- "taking out" popular and well-respected governors, legislators, etc., who do not have access to nearly as much funding, by distorting or outright lying about their records
- influencing the outcome of ballot measures (which can draw one side or another to the polls)
- suppressing voter turnout by spewing negativity