That Mitt Romney has a massive war chest is obvious at this point, but on occasion, it still comes as a surprise to see how much he outspends his opponents. This chart from Buzzfeed shows the extent to which Romney has buried his competitors:
This is one reason I've always been reluctant to predict success for any of Romney's competitors in the Republican primary. The ability to spend this much money is a huge advantage, and while it doesn't guarantee victory, the only challenge could come from someone with deep pockets, deep party support, a superior organization, or both. As it stands, Mitt Romney has been the only candidate to fit either bill, which is why it's always been safe to bet on his eventual victory.