CAMBRIDGE • On Jan 20 next year, Mr Donald Trump will be sworn in as the 45th President of the United States. I say "sworn in" rather than "assume the presidency" because under Section I of Article II of the US Constitution, Mr Trump cannot actually become president unless he takes an oath of office, publicly committing himself to uphold the Constitution and perform to the best of his ability while in office. That is, of course, the case for all presidents. But given how he comported himself during the campaign, it is particularly meaningful in his case.
Until now, Mr Trump has made no effort to behave in an honest or reliable way. Technically, he didn't have to. The US does not require any sworn statements from the men and women who run for president, nor does it have any enforceable code of behaviour or constraints on the kind of rhetoric that can be used. Candidates may conduct themselves however they see fit.
This approach is based on the assumption that we can trust the candidates' judgment. People seeking the country's highest office should know how to balance the political imperative of winning votes with a sense of responsibility for the feasibility of - and reasoning behind - their policy promises.
By and large, experience has vindicated this view. The US has had the good fortune of choosing largely from among presidential aspirants who adhere to generally accepted norms.
With Mr Trump, it seems that fortune has turned into bankruptcy.
During his primary and general election campaigns, he lied incessantly about himself, his businesses, his opponents, other countries' behaviour and motivations, America's electoral system, the size of trade deficits, the actions of the Federal Reserve, and data on everything from labour to crime (to name a few examples).
Moreover, many of his campaign promises - building a Mexico-funded wall on America's southern border, bringing back lost manufacturing jobs, deporting millions of illegal immigrants - are patently impossible to implement. Mr Mitt Romney, the Republican Party's presidential nominee in 2012, was right when he called Mr Trump "a phony, a fraud", a candidate whose promises are "worthless".
But while these traits are clearly problematic, they obviously have not hurt Mr Trump's political career. He convinced a sizeable portion of the electorate to ignore - if not condone - his flagrant policy reversals and lack of knowledge. Even Mr Romney himself bowed to Mr Trump in the end, meeting the president-elect a couple of weeks after the election, reportedly in search of a Cabinet position.
This has to be one of the most sobering lessons from this past year: Outrageous lies and hollow promises can win even the most consequential elections. And adhering to basic norms of decency - facts can be massaged but not manufactured, and promises must be plausible, if vague - can lose them. Mr Trump's opponent in the campaign, former Secretary of State Hillary Clinton, learnt that the hard way.
During the campaign, Mrs Clinton often quoted First Lady Michelle Obama: "When they go low," she would declare, "we go high." But when your opponent goes as low as Mr Trump, "going high" is like choosing, in a classic prisoner's dilemma, to remain loyal to your partner in crime, who, sitting in the next room, is cutting a deal to testify against you. When you "go high" in such circumstances, you get what game theorists call a "sucker's payoff".
Candidates should never be put in such a position. Instead, we must make sure that all candidates adhere to a basic code of conduct. One simple way to do that would be to demand all presidential candidates, beginning in 2020, take an oath to be truthful, responsible and transparent in their campaign rhetoric and conduct.
In American society and political culture, the oath has a rare status. Testifying in a court of law or before a committee of the US Congress, witnesses "solemnly swear to tell the truth, the whole truth and nothing but the truth". Doctors take the Hippocratic Oath pledging first to do no harm. Students at many universities swear to uphold an honour code. And Mr Trump will not be alone in taking his oath next month: At around the same time, new members of the Congress and Mr Trump's Cabinet will make a similar pledge.
Given this reverence for oaths, it is reasonable to assume that taking a truthfulness oath before initiating a campaign for public office would have some impact on candidates' approach.
There is nothing partisan about this proposal; many Republicans were victims of Mr Trump's unbridled campaign style before Mrs Clinton was in his crosshairs. The public and the media could use the oath as a tool for assessing - and holding accountable - would-be leaders. And candidates would stand to gain a competitive advantage against opponents who refuse to take the oath.
Implementation would not be difficult. While the presidential oath is required by the Constitution, a candidates' oath wouldn't have to be. Political and market pressure would be enough, if print, television and social media simply refused to carry campaign advertisements from candidates who refuse to take the oath.
The political advantage should not go to the most mendacious candidate. For the sake of democracy, we must take action to solidify basic norms of decency and transparency in vital election campaigns. We can start with the modest step of demanding a truthfulness oath from all future presidential candidates.
PROJECT SYNDICATE
•Yasheng Huang is Professor of Global Economics and Management at MIT Sloan School of Management.
