Arizona has way too many Mormons for Romney to lose there. I don’t know what Santorum was thinking, appearing at a debate in Mesa, with the high percentage of Mormons in that town.
Mormon's stacked the audience during the debate and whooped and cheered at every Romney platitude. They are a big factor and likely vote more Republican than Democrat (Harry Reid excepted). In fact, the Mormon temple in Mesa has the biggest attendance of any outside of Utah. The LDS population in the PHX area has led to the building of two more temples that will open in the next two to five years. If Santorum can cut Romney's lead or even defeat him there (as unlikely as it seems), Mitt will have trouble going forward in areas less populated by them.