Newt isn’t running against Santorum. He’s running against Romney and Obama. You should ask yourself and Santorum if he is running against Gingrich or Romney/Obama.
In my opinion, Newt IS running against Santorum to determine which of them will unite the Conservative vote to defeat Romney. A series of one-on-one Lincoln-Douglas debates between those two--hosted by conservatives--is exactly what we need.
I am surprised we have not heard more about Santorum challenging Newt to a one-on-one.