How often do you hear about someone who has been living with, taking care of, and bragging to everyone about what a wonderful friend he has. One day this friend turns on him, and he finds himself running for his life.
This is what happened to Eric Cantor. After kowtowing to the tea party for years, he was found to be ideologically impure and the tea party turned against him.
A political party that judges your worthiness for office by your ideological purity can't be trusted. Just ask Eric Cantor.