Mitt Romney released his campaign’s cash figures Thursday, showing that he had $7.3 million on hand at the end of February. Since he raised $11.5 million last month, and he had $7.7 million at the end of January, it means that he only spent $11.9 million in February to fight off a huge challenge from Rick Santorum and win Nevada, Michigan, Arizona, and set up his Super Tuesday victories. It shows Romney’s strong reliance on super PACs and his personal wealth. Santorum has said he raised $9 million in campaign funds in February, far more than in any previous month. (He’s reportedly raised only $16 million total so far.) If true, it’s more evidence that Romney is looking even stronger, since his spending was way down from January ($18.8 million) and he still managed to hold off Santorum’s surge.