Not sure I understand your post. Gingrich has not campaigned in either Michigan or Arizona to give Santorum the edge in the “not Romney” vote. He certainly is not waging this strategy to help Romney.
Dems are voting Santorum in Michigan because they think he will be easier to beat than Romney.
If so, the Dems are in for a big surprise. Santorum as nominee will energize the base, sweep the south, and carry most if not all of the rust-belt states and won’t be carrying the RomneyCare albatross around his neck. He is in today’s USA-Gallup leading Obama by a point or two.
But none of the polls or articles I’ve seen has referenced Dems voting for Santorum- so what’s the source for this?