In the late 1960s, at a point when he was furious with those who had thwarted his White House ambitions, Nelson Rockefeller told a group of conservative Republicans, "I'm a hawk on foreign policy, I'm a conservative on the economy, and I'm a dove on social matters. You've got two-thirds of me. What more do you want?" Their answer, of course, was "everything," which Rocky wouldn't, or couldn't, deliver.
A decade later, another moderate Republican seeking the presidency applauded Rockefeller's stance. "Two-thirds should be more than enough to gain the nomination," George Bush said in 1979. But as it wasn't for...