This is when grace leaves the White House. Without talking about politics or policy, without getting into race or class, red or blue, the Obamas set a remarkable standard for personal decency and civility during their years as the United States' first family.

The Obamas came in making history, changing the US on day one. They were the first African-American occupants of the country's most famous address, a home slaves helped to build.

Few families have faced such scrutiny. Would they be too black? Would they be too white? How on Earth would they satisfy a nation of people who cry with joy at the sight of their faces and want them dead because of the colour of their skin?

Their eight years in the White House were a master class in dignity and tolerance.

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And it's easy to forget that now.

Because now is the time when the historians and pundits measure a commander in chief's legacy on the abacus of accomplishment. And political Washington is busy either dismantling or defending eight years of President Barack Obama's policies.

The Affordable Care Act, the Paris climate agreement, the Iran nuclear deal - all of these are under attack from Donald Trump and the Republicans in Congress. Much of it could vanish.

And if that's the case, what were those eight years for?

The arc of history bends toward a different and enduring legacy that Obama and his family leave: decency.

There have been no terrible scandals. No Lincoln bedroom shenanigans, no blue dress, no Watergate plumbers, no psychics, no Teapot Domes. No strippers, no divorces and no illegitimate children (Did you know that five presidents had those?).

Maybe we've lost all shame. Maybe we demand so little of ourselves and our elected leaders that we are thunderstruck when we encounter people who don't behave like Real Housewives or Kardashians.

The Obamas maintained their poise in the face of relentless bile. Over the past eight years, it was impossible to speak or write a single word about the family, the Oval Office, the White House or even their dogs without a blast of racially charged, historically repugnant hate coming their way.

Obama was depicted in cartoonish tribal costumes, Michelle Obama was called an ape in heels, football fans thought it would be funny to dress as the President in a noose.

Dozens of people have been indicted on charges of threatening to harm the Obamas while they were in the White House. In 2011, a gunman fired at the family's home, lodging seven bullets into the walls when one of the Obama girls and her grandmother were home.

A fence jumper armed with a knife made it past security and all the way into the home before he was tackled by an off-duty agent.

The numbers vary, but some security sources said the Obama family faced three times as many threats as other first families.

The biggest scandal in the White House while they lived there was the Secret Service's breakdown in protecting them.

And facing all that, they never lashed out. They never tweeted their anger, derided their enemies or hit back with something harder and nastier.

"When they go low, we go high," Michelle Obama said repeatedly. And she meant it.

The family's refusal to engage in ugliness was almost old-fashioned, in a world dominated by what the Washington Post's Sarah Kaufman calls the "grace gap". "Our impatient, fragmented, competitive society conspires in many ways against gentleness and understanding.

"Popular culture stokes delight in humiliation and conflict," Kaufman wrote in her book The Art of Grace. American society is increasingly defined by the Me Generation, the Be Yourself Generation and the reality show puppeteers.

It's a selfie, manspreading, mean-spirited culture - and the attack on civility is being led by the next occupant of the White House.

One of mankind's oldest books, written in Egypt 4500 years ago by a pharaoh's adviser named Ptahhotep, is an early Miss Manners column on how real leaders should behave, Kaufman says.

"If thou be powerful, make thyself to be honoured for knowledge and for gentleness," Ptahhotep wrote.

That gentleness earned Obama plenty of scorn from those who read it as weakness.

But it's no secret that the pulled punch and the turned cheek take far more courage and character than a reptilian lash-out.

No, instead of petulance or cowardice, the Obamas taught us decency, forgiveness, courage - values that are the bedrock of American greatness.

The nation has seen grace.

And now more than ever, we must remember it.