As he's a "mainlander" (外省人, i.e. at least one parent came over with Chiang Kai-shek following the 1949 loss to the Chinese Communist Party in the Chinese Civil War)the Mazu reference seems to be something meant to appeal to Taiwanese (本省人) voters, kind of like a presidential candidate in the U.S. claiming strong local ties when traveling to different regions where that plays well. Yes, he's religious, and he speaks Taiwanese, but I wouldn't assume a huge number of Taiwanese people will back him for those reasons alone.
If Gou has real support from the KMT -- no easy thing, considering he hasn't been heavily active in local politics AFAIK -- he might get some wind in his sails, particularly if he sticks with the practical themes relating to cross-strait trade and economic growth. He understands that very, very well.
If he doesn't have the right political network in place, though, he's going to piss off a lot of KMT people and likely to relegated to the margins -- or siphon off a lot of blue supporters for an indie run, which will lead to the same type of situation the U.S. Republican party had back in the 90s with Ross Perot.