It was tempting to believe history had turned a page. Alas, posterity may see Barack Obama’s 2008 election as a detour from the path an angry America took after 9/11. Mr Obama called for an open dialogue with the Muslim world. Donald Trump and his team have all but declared war on Islam. Mr Obama believed there was no problem that could not be salved by reason. Mr Trump has opposite instincts. Whatever precise form Mr Trump’s administration takes, we know this: Mr Obama’s legacy will be purged. In many cases all it will take is the stroke of Mr Trump’s pen.

The Obama erasure will go far deeper than undoing domestic laws, or foreign deals. Mr Trump will repeal Obamacare, or alter it beyond recognition. He will “keep an open mind” about whether to pull the US out of the Paris agreement on climate change and quite probably blow up the US-Iran nuclear deal. These acts would undo Mr Obama’s most visible achievements. Less obvious ones, such as the ban on Arctic drilling and enhanced interrogation techniques and the intention of closing Guantánamo Bay (never completed) will also be consigned to the dustbin. It will be as if Mr Obama was never here.

The bizarre thing is that the same America which elected Mr Trump is already missing Mr Obama. This often happens to outgoing presidents. But in Mr Obama’s case it is unusually sharp. At 55 per cent his job approval is equivalent to Ronald Reagan’s at the same point, and ahead of Bill Clinton’s. It is more than 20 points higher than George W Bush’s. The more Mr Trump tweets from the gut, the more Americans appreciate Mr Obama’s calm weighing of pros and cons. “No drama Obama” is even making the case that Mr Trump be given a chance to succeed. “I think nothing is the end of the world until it is the end of the world,” he told the New Yorker.