Why doesn’t he run as a democrat? And why doesn’t the republican party tell him to get out?
1. Because he is a Progressive Republican
2. The republican party is about to tell him to get out. In the primary elections. Mittens knows this. That is why he feels compelled to come out of the liberal closet now. That is all there is to it.
In 1992, Romney, after switching to Independent in the 80s because of Reagan, was only giving to, and fund raising for, Democrat candidates, it was 1993 when he registered Republican so that he could run for the Senate.