These former leaders would like it thought that high principle keeps them away from a GOP convention that would nominate Donald Trump. Petulance, however, must surely play a part. Bush Republicans feel unappreciated, and understandably so.

For Trump's nomination represents not only a rejection of their legacy but a repudiation of much of post-Cold War party dogma.

America crossed a historic divide and entered a new era. Even should Trump lose, there is likely no going back.

Trump has attacked NAFTA, MFN for China and the South Korea trade deal as badly negotiated. But the problem lies not just in the treaties but in the economic philosophy upon which they were based.