Sen. Jim DeMint is making a bid to be the tea party movement’s best friend in Washington. It’s hardly a coincidence that the South Carolina Republican finds himself with few friends in his own workplace. DeMint — ideological warrior, cable TV regular, possible 2012 presidential candidate — is trying to channel the anti-establishment passions roiling the conservative movement while serving in the U.S. Senate, which even in a more raffish age of politics still counts as the most establishmentarian institution in American life. Examples of his senatorial poor form keep growing. DeMint has refused to endorse some of his fellow...