This doesn't even mention the fact that both Romney and McCain were in serious danger of losing the nomination due to a perception that they were for amnesty, and I expect it to be no different for Bush.
Romney was never in danger of losing the nomination because of a "perception that he was for amnesty". He was in danger of losing the nomination because of healthcare, his flip flops on abortion and guns, and his image as an establishment guy. Romney had been defined by his running against Rudy and McCain on the illegal immigration and most of his tea party opponents were weaker than Romney on the issue (Perry and Gingrich for instance) and only Santorum had a record that was arguably stronger than his. Romney used the issue to leverage and outflank his more conservative opponents and proved that base votes value it as high as the top three to the extent that candidates far more conservative than Romney were rendered "imperfect" and thus no better then Mittens by virtue of them being weaker on it.
