Former President Barack Obama's decision to accept a $400,000 fee to speak at a health care conference organized by the bond firm Cantor Fitzgerald is easily understood. That's so much cash, for so little work, that it would be extraordinarily difficult for anyone to turn it down. And the precedent established by former Presidents Bill Clinton and George W. Bush, to say nothing of former Federal Reserve Chairs Ben Bernanke and Alan Greenspan and a slew of other high-ranking former officials, is that there is nothing wrong with taking the money.

Indeed, to not take the money might be a problem for someone in Obama's position. It would set a precedent.

Obama would be suggesting that for an economically comfortable high-ranking former government official to be out there doing paid speaking gigs would be corrupt, sleazy, or both. He'd be looking down his nose at the other corrupt, sleazy former high-ranking government officials and making enemies.

Which is exactly why he should have turned down the gig.

The election in France earlier this week shows that the triumph of populist demagogues is far from inevitable. But to beat it, mainstream politicians and institutions need to shape up — not just with better policies, but with the kind of self-sacrificing spirit and moral leadership that successful movements require.

That means some people are going to have to start making less money and raising the ethical bar for conduct, rather than leveling down to the worst acts of their predecessors.

Mainstream leaders need to step up

The fundamental concept of Donald Trump's ethnonationalist demagoguery is that white middle-class Americans are locked in a zero-sum conflict with foreigners and ethnic minority groups. That's Marine Le Pen's message in France and Geert Wilders's message in the Netherlands, and it is ugly and false.

A counterproposal on the left is to reframe the populist theme and argue that middle-class Americans more generally are locked in a zero-sum conflict with rich people.

Obama and other center-left leaders around the world do not espouse that view primarily, I think, because they believe it is simplistic and wrong. But a crucial vulnerability of center-left politics around the world is that their sincere conviction — a faith in the positive-sum nature of cosmopolitan values and appropriately regulated forms of global capitalism, tempered by a welfare state — is easily mistaken for corruption. The political right is supposed to be pro-business as a matter of ideological commitment. The progressive center is supposed to be empirically minded, challenging business interests where appropriate but granting them free rein at other times.

This approach has a lot of political and substantive merits. But it is invariably subject to the objection: really?

Did you really avoid breaking up the big banks because you thought it would undermine financial stability, or were you on the take? Did you really think a fracking ban would be bad for the environment, or were you on the take? One man's sophisticated and pragmatic approach to public policy can be the other man's grab bag of corrupt opportunism.

Leaders who sincerely care about the fate of the progressive center as a nationally and globally viable political movement need to push back against this perception by behaving with a higher degree of personal integrity than their rivals — not by accepting the logic that what's good for the goose is good for the gander.

Corruption is the progressive center’s Achilles’ heel

Perhaps my wrongest take of the 2016 campaign was issued right before Election Day, when I acknowledged that in the abstract Nate Silver was right that Hillary Clinton wasn't a lock in the Electoral College but dismissed Donald Trump's chances anyway because of Obama's high approval ratings. Undecided voters would never break for Trump under those circumstances, I thought, since Obama and Clinton were so ideologically similar.

And so they were. But the gap between them on issues of corruption and personal integrity was enormous. The Clinton family had earned tens of millions of dollars over the years thanks to buckraking speaking fees that raised fundamental questions in people's minds about the motives of both their public policy and their philanthropic work. The Obama family hadn't.

You see from the success of Emmanuel Macron in France and Justin Trudeau in Canada (or before them Helle Thorning-Schmidt in Denmark) that center-left politics remains perfectly viable around the world when its leaders are trusted. But you also see from the ongoing meltdown of the UK Labour Party how the perception that Tony Blair used his prime ministership primarily to vault himself into the ranks of the global financial elite can poison a political tendency's reputation. The Blair years saw historic reductions in inequality and child poverty, but Blairism has become a swear word to Labour's own members because it is seen as lacking integrity.

Populist nationalists, for better or for worse, are held to a lower standard in this regard precisely because they are committed to a zero-sum politics. As Princeton University’s Jan-Werner Müller writes in his excellent short book on populist authoritarianism, “[T}he perception among supporters of populists is that corruption and cronyism are not genuine problems as long as they look like measures pursued for the sake of a moral, hardworking ‘us’ and not for the immoral or even foreign ‘them.’”

Ethics rules will never be enough

Beyond politicians' speaking fees, people are, of course, troubled by larger questions of revolving doors between the private and public sectors. What would be nice would be to devise some convenient bright-line rule presidents could propose that would prevent the government from being suborned by special interest.

Realistically, it can't be done. "Nobody can ever work in the private sector before or after joining the government" isn't a viable rule. What's troubling isn't any one specific case. It's the sheer accumulation of them, leading to the perception that service in Democratic Party politics was viewed in general as just a stepping stone to a higher-paid gig in New York or Silicon Valley.

But the difficulty of drawing a clear, overarching ethical line is exactly why an ex-president, who is uniquely high-profile and uniquely insulated from financial pressures, ought to set a high standard. Obama doesn't need a next job. As a former president, he is entitled to lifelong health care and a pension worth more than $200,000 a year. He's already written two best-selling books and could easily write a third or fourth. (A recent deal between the Obamas and Penguin Random House will reportedly earn the former first couple at least $65 million.)

Obama has already raised millions for his library and presidential foundation. He, more than any of his former subordinates, can safely say no, that Harry Truman was right and this is an unseemly thing for a former president to be doing, and that it was a mistake of American society to normalize that form of conduct from his immediate few predecessors.

Change we can believe in

In an unpaid speaking appearance earlier this week at the University of Chicago, Obama demonstrated his enduring faith in both the American people and his brand of politics. He explained that the progressive views of younger Americans give him hope and that he wants to make it the primary mission of his post-presidency to break down the barriers that dissuade young people from participating in political life.

It's a fine vision, one that successfully walks the line between post-presidential high-mindedness and partisan politics.

Obama should take seriously the message it sends to those young people if he decides to make a career out of buckraking. He knows that Hillary Clinton isn't popular with the youth cohort the way he is. And he knows that populists on both the left and the right want to make a sweeping ideological critique of all center-left politics, not just a narrow personal one of Clinton. Does Obama want them to win that battle and carry the day with the message that mainstream politics is just a moneymaking hustle?

Of course, it's just one speech. Nothing is irrevocable about one speech. But money doesn't get any easier to turn down with time, any more than rebuking friends and colleagues gets easier. To make his post-presidency a success, Obama should give this money to some good cause and then swear off these gigs entirely.