According to RNC rule 40(b):
"Each candidate for nomination for President of the United States and Vice President of the United States shall demonstrate the support of a plurality of the delegates from each of five (5) or more states, severally, prior to the presentation of the name of that candidate for nomination."
. . . which means that Newt, who has won in two states thus far (South Carolina and Georgia), must win a minimum of three more states (and it doesn't matter which three) in order to become eligible in a brokered/contested convention.
Further, that means that Santorum (who legitimately won binding public contests in Oklahoma, Tennessee, Kansas, Alabama, and Mississippi) has enough states committed to him to qualify at the now-seemingly-inevitable convention floor fight.
Romney, of course, has binding pluralities locked down in Nevada, Alaska, Massachusetts, Vermont, Virginia, Hawaii, and Puerto Rico (as well as Florida and Arizona, even if the appeals are upheld).
Ron Paul, on the other hand, has binding pluralities locked down in . . . umm . . . nowhere that I can identify.