Romney raised the bulk of his money from big-dollar donors in February; only one in 11 dollars he raised came from those who donated $200 or less.

The former Massachusetts governor spent at an aggressive pace in February, dropping $12.3 million on races in Michigan, Nevada, Colorado and elsewhere. But it was one-third less than what he spent in January, where expensive contests in Florida, New Hampshire and Iowa drained all the candidates' resources. Romney had almost $20 million on hand at the beginning of January.

Romney spent tens of millions of his own money on his 2008 campaign, but has contributed just $52,500 to his campaign this cycle, Federal Election Commission documents show.