Until the day she died, Barbara Bush kept a clock next to her bed that counted the days until Donald Trump was gone.
The former first lady's timekeeping was upbeat: she assumed a one-term presidency. Most of the world is in the late Bush's camp.
To judge by the absence of diplomatic initiatives, the west is also marking the calendar until Trump leaves office. The same goes for non-Trumpian America. As Joe Biden, the Democratic frontrunner, keeps saying, Trump is an "aberration" — as though time has briefly gone astray. All we need is to wait out the clock then reset it.
There are two problems with this view. The first is that you cannot recapture lost time. The world will not reboot to where it was before Trump took office. A defeat for Trump would be bad news for Saudi Arabia, Russia and North Korea. Trump has licensed Saudi adventurism, validated Vladimir Putin's world view, and given Kim Jong Un a coming-out party to remember.
But it is unclear Trump's exit would make much difference to China. The most striking change to have happened since he took office is the speed with which Washington has embraced the so-called new cold war. Trump's successor would be as likely as he to see China as America's main rival.
Europe, Japan, Canada and Australia should also be wary. Although Trump's departure would herald a big change in tone, there would be continuities on substance.
Trump's Democratic successor would be just as impatient with Europe's low defence budgets. Polls that show most Americans in favour of free trade are misleading because they miss the intensity of opposition.
Decisive factions on both ends of the spectrum are strongly opposed to new deals — with allies or others. In the past, Democratic presidents could rely on Republican lawmakers to pass their trade deals. Those days are probably over. The logical step for any US president to contain China would be to rejoin Barack Obama's Trans-Pacific Partnership.
Yet even Obama could not persuade Democrats to vote for the TPP. It is doubtful a President Elizabeth Warren or a President Kamala Harris would even try. Warren's foreign policy has been called "Trumpism with a human face".
The exception to waiting out the clock is Iran. Last week its supreme leader, Ayatollah Ali Khamenei, dismissed any thought of negotiating with Trump. The implication should have been that Iran would wait until America elected someone less erratic.
Yet Iran is ignoring Europe's advice to stay within the nuclear deal. It plans to start breaching its enrichment limits this weekend. Whatever the dangers of a US-Iran conflict, the situation cannot go back to before. Iran will either be at war with the US when the next president takes office, or a year and a half closer to being a nuclear power. Possibly both. That clock cannot be reset.
The second problem with the "aberration" school is that Trump might win a second term. History says US presidents are re-elected if the economy is growing. The only one-term presidents in the past 100 years were George H.W. Bush, Jimmy Carter and Herbert Hoover. Each was grappling with a recession. Trump may be an exception to that rule. Or the US economy could take a nosedive. Betting on either would be rash.
Meanwhile, the chances are that Trump's opponent will have taken enough outlandish stances to improve his re-election prospects sharply. In last week's Democratic debates, many candidates vowed to abolish a law that criminalises illegal border crossings. The US public is generally pro-immigration.
But it strongly opposes open borders. Three leading candidates wanted to abolish private health insurance. Most also support a bill that would give transgender bathroom choice for children. These are the positions Trump wants in his opponent.
Which leaves the run-down-the-clock crowd in a quandary. On the one hand, the world might be stuck with him until 2025, in which case it will have wasted four years betting that America had erred.
On the other, Trump's defeat would not recreate the world they think they remember.
As the saying goes, you cannot step into the same river twice. Either way, America's allies should hope for the best but work far harder to prepare for the worst.
Written by: Edward Luce
© Financial Times