President needs to sell continuity we can believe in

optimism about the opposition he would face. “I could stand up here and say: Let’s just get everybody together, let’s get unified,” she said. “The sky will open, the light will come down, celestial choirs will be singing, and everyone will know we should do the right thing, and the world will be perfect.”

She added: “Maybe I’ve just lived a little long, but I have no illusions about how hard this is going to be.”

Both of them have now lived a little longer and both have seen how the relentless oppositionism of the Republican Party led inexorably to Trump, the most dangerous and irresponsible nominee any major political party has ever put forward. Never before has a candidate asked a foreign power to conduct espionage on the United States, as Trump did on Wednesday. “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing,” he said. Never before has a campaign become a national emergency.

This alone would justify Obama’s passionate intervention on Clinton’s behalf. But there is more: Both find themselves on the same side of internal Democratic arguments about how change is achieved, and how fast it can come. Both must grapple with an impatience embodied in Bernie Sanders’ campaign and his call for a political revolution. The truth is that both Obama and Clinton were always evolutionists and reformists, always about the politics of the possible.

Fortunately for them both, Trump presents such a radical departure from anything the political system has seen that he has vastly simplified Obama’s task. The president’s brief for Clinton rests less on ideology than on her sense of responsibility and her preparation for the job. He can argue that the election of her opponent presents incalculable risks for a country that, judging from his approval rating, has on the whole come to appreciate his approach.

Obama and Clinton are more than ever bound to the same argument: The changes Trump threatens are not the ones the country should want, and the changes the country does want would only be possible under Clinton.

Thus will a leader who won office promising “change we can believe in” turn to the task of defending continuity we can believe in. Dear Hillary, Donald Trump has presented you with an amazing opportunity to become a world historical figure! If you crush him in this election, you could create a new Democratic majority and reduce the GOP to an ever-declining rump of ethnic nationalism. On the other hand, if you fail to beat Trump, you will go down as America’s most hapless political loser and be vilified forever for enabling an era of American Putinism. No pressure! To end up on the right side of this equation you’re probably going to have to resist three natural tendencies, two of them your party’s and one your own.