Funny how quickly some principles collapse when given the right kind of shove. One day, the Republican Party is rock-ribbed restrictionist, order dedicated to the proposition that unauthorized immigrants are an invading army of job stealers, site welfare moochers and criminals whose only acceptable destiny is to be caught and deported — the border fence forever, “amnesty” never. The next day: never mind. The party suddenly discovers the merits of a working immigration system. Senators like John McCain and Lindsey Graham, who once bravely supported bipartisan reform but slunk away late in the last Bush administration, are scratching at the door again, as if the last five years never happened. This poses an opportunity and a challenge for Mr. Obama, who promised to tackle immigration reform in his first term and did not, and is firmly on the hook to do so now. He says he will push reform early, and he looks well positioned to get something done.