Santorum's lifetime rating was an 88.1 (as of 2006, his last year in the Senate). That puts him among the more moderate half of Republican senators at the time -- and to the left of Lindsay Graham, John Sunnunu, Elizabeth Dole and Trent Lott.
Upshot: Santorum is a social conservative -- not a fiscal one. What's more, as I've said before, the problem with his formulation of social issues is that (despite Santorum's best intentions) they come off as preachy, judgmental and off-putting. In part, perhaps that's because he can't seem to help approaching them as theological, rather than social, issues.
And -- fatally in this year when Americans are rightly preoccupied with the economy -- they are a distraction. The newest example is the kerfuffle over speaking English in Puerto Rico. Can you imagine how much President Obama is loving this stuff? He can only dream of an autumn discussing bilingualism and contraception -- rather than his failed economic stewardship, budget-busting ObamaCare, Iran's nukes, and expensive gasoline.
The only way that Santorum is the only "real" conservative in the race is if in-your-face social conservatism is somehow "more equal" than any other kind.