There are many theories about campaign spending. Many (if not most) say it is relatively infective. (Erickson & Palfrey, 2000) Others claim that it does have an effect, but small: one percent increase for doubling the spending. Some claim that it differs for incumbents vs challengers, usually stating that incumbents spending is less effective, while challenger spending more so - in large part because challengers have to do more. Incumbents have a large advantage particularly in simple name recognition. (Abramowitz 1988, Gergber 2004.) But almost all of them state that the higher the election, the less effective money becomes. At the presidential level, if money does anything at all, it takes an awful lot of it to get any results.
I personally am of the opinion, that cause and effect are being reversed. Money does not buy winning votes for in an election, instead winning candidates attract money. Campaign finances are not shady, despicable things, but instead the best polls you get for free. People vote with their wallet before they vote at the booth. The most popular guy gets the most money and then goes on too win, as opposed to the other way around.
In any case, Obama clearly has a lot more money than the GOP candidates. (http://elections.nytimes.com/2012/campaign-finance?hp) The NY Times says Obama has raised almost $100,million, as compared to Romney's, $32.6 million. The entire Republican field has raised a total of $90.1 million. That is still 10% less than Obama and that includes the Ron Paul people and the Cain people, neither of whom are likely to give freely to any other candidate but their own.
Best of all, Obama raised 52% of his money from small donations (under $200), as compared to Romney, who got 61% of his cash from maximum donations ($2,500). Romney got less than 10% of his money from small donations and Obama got only 22% of his from maximum donations. But not that 20% of $100 million is still more than 61% of $33 million
Last year, at this same time period, Clinton was the rich woman at $62,7 million, vs Obama at $58.6, Romney at $43.5, Giulani at $34.4 and McCain at $25.9. Romney did better 4 years ago than he is doing now and lost the Primary, to McCain, who lost the general election.
Obama, despite his poor showing in the polls, is going to win the 2012 election. Not because he is going to buy the election, but simply because so many people want him to win. The voters are voting with their pocketbook and giving him money and LOTS of it, mostly in small batches of less than $200.
The Republicans are caught up in pandering to the far right, ignoring the moderates that are essential to win the presidential election. The T-Party won't let them pick anyone that can beat Obama, their strategists are ignoring the needs and desires of the majority of the citizens of the USA, and blaming Obama for everything bad, while it sells well to their base, just angers the undecided.
Part of the problem is that blaming the other guy does not win you votes, ever. Politicians have a bad reputation. We don't like them. To quote South Park: "But Stan, don't you know, it's always between a giant douche and a turd sandwich. Nearly every election since the beginning of time has been between some douche and some turd." The fact that Obama is hated by the far right means nothing, the fact that the left is angry with Obama for not doing enough, means nothing. The fact that our opposing choice is WORSE is what matters.
Another issue is the plan. People vote for a guy with a plan, not the guy that says the plan sucks. For the GOP to win, they need to shift the rhetoric away from how bad Obama is, and about how good their plan is. Too bad their only plans are rehashes of old stuff that people don't believe in. To shift the rhetoric, you need not just a plan, but a NEW plan. Which is something they have not had in 10 years.