Image copyright Getty Images Image caption Donald Trump: no ordinary president

One of my cherished possessions, which I cart with me around the world, is a tattered paperback copy of the Penguin Book of Twentieth-Century Speeches.

On the front cover, John F Kennedy stands gripping a lectern, in full flow; on the back, Martin Luther King raises a hand before the crowd at the Lincoln Memorial in Washington DC.

As you gaze at that second picture, you can hear his preacher's voice, resonant and rhythmic. You can hear the cadences rise and fall, a hint of vibrato, as he describes his dream.

On the pages in between, the speeches shine brightly with democratic ideals, many proclaimed by American presidents.

There is Woodrow Wilson, promoting the League of Nations in Pueblo, Colorado in September 1919: "There is one thing that the American people always rise to and extend their hand to, and that is the truth of justice and of liberty and of peace."

There is Herbert Hoover's great rallying cry for conservatism in New York in October 1928: "The march of progress" founded on "ordered liberty, freedom and equal opportunity to the individual."

The Wall Street crash of the following year brought that march to an abrupt halt, and by the spring of 1933, when Franklin Delano Roosevelt's inauguration speech crackled across the radio airwaves, the nation was in the desolation of the Great Depression.

Roosevelt's watershed inaugural is best remembered for its signature line - "the only thing we have to fear is fear itself" - but it contained much else besides, not least a warning of the "false belief that public office and high political position are to be valued only by the standards of pride of place and personal profit".

A Democrat, Roosevelt might have abjured the "rugged individualism" of his Republican predecessor, but the two presidents shared a commitment to liberty, characterised by Roosevelt in his 1941 address to Congress as "four freedoms": namely the freedoms of speech and religion and freedoms from want and fear.

"Enduring peace cannot be bought at the cost of other people's freedom," he declared.

Image copyright AFP Image caption Martin Luther King waves to supporters from the Lincoln Memorial, 1963

Roosevelt had a year earlier started his country on the long, slow turn away from isolationism and toward engagement in the fight against fascism, with his "arsenal of democracy" speech, in which he urged reluctant citizens to lend their vast resources to the British war effort.

Thirteen presidents later, the debate about whether to turn inward or to engage with the world has been resurrected by Donald Trump. He insists that he is not an isolationist but he describes US foreign policy in unilateral, transactional terms and has championed "America First" — a phrase originally associated with opposition to Roosevelt's desire to fight Hitler.

The most prominent spokesman for the 1940s America First Committee, the celebrated aviator Charles Lindbergh, accused Jewish groups of "agitating for war" and was himself accused of being pro-Nazi.

Embracing the phrase "America First" does not in itself indicate fascism, but there is more to the picture than that.

For Lindbergh and Roosevelt, the Japanese attack on Pearl Harbor changed everything. In 1944 American troops waded through the surf of Normandy's beaches and into the path of Nazi bullets.

Half a lifetime later, at Pointe du Hoc on the English Channel, Ronald Reagan commemorated their sacrifice with the words: "Here the Allies stood and fought against tyranny in a giant undertaking unparalleled in human history." That's in my book of speeches too.

Of course, the United States has not always lived up to its own ideals.

This week marks the 153rd anniversary of the Sand Creek Massacre, when US troops murdered and mutilated women and children of the Cheyenne and Arapaho tribes in Colorado, just one atrocity among many as white Europeans vanquished the native peoples of the New World.

Then a country founded on genocide and slavery covered its ears for shameful ages before it heard Martin Luther King's insistence that it "make real the promises of democracy" for African Americans. Woodrow Wilson, for one, used fine words but he introduced racist policies too. Even now, that promise of democracy remains only partially fulfilled.

The US has been guilty of bombing civilians, of torture and imprisonment without trial and of subverting the very democracy it professes to hold sacred when it does not like what democracy delivers.

Image copyright AFP Image caption Trump has praised authoritarian leaders like Rodrigo Duterte of the Philippines

The 45th US president appears to recognise some of this. Shortly after taking office, Mr Trump told Fox News that he respected the Russian president Vladimir Putin.

The interviewer objected: "He's a killer though. Putin's a killer."

"There are a lot of killers," Mr Trump replied. "We've got a lot of killers. What, you think our country's so innocent?"

He may have been correct, but for an American president to casually and publicly equate his country with Putin's Russia was nonetheless a stunning and revealing moment.

For much of its history, America's leaders have, at the very least, paid lip service to upholding the virtues on which their nation was founded - often in the face of existential totalitarian threats, not least from Moscow.

"Freedom has many difficulties and democracy is not perfect," President Kennedy acknowledged in Berlin in 1963, "but we have never had to put up a wall to keep our people in, to prevent them from leaving us."

Mr Trump's rhetoric has been rather different.

Far from prioritising freedom of religion and racial reconciliation, he has repeatedly played to a gallery of the far right. He spread the racist lie that Barack Obama was not born in the US.

He has sought to undermine the free press, repeatedly dismissing inconvenient or critical journalism as "fake news".

He has cosied up to autocrats, from Turkey's Erdogan ("very high marks") to Duterte of the Philippines (a "great relationship") to Egypt's Sisi ("love your shoes").

His reaction to news of a terrorist attack in London was not to express solidarity with the mayor of the city, Sadiq Khan, but to attack him. Mr Khan is a Muslim.

And now, in perhaps the most shocking move of all, Mr Trump has used his Twitter account with more than 40 million followers to deliver a huge boost to Britain First, a racist group on the far-right fringes of UK politics, and followed up with an attack on the British prime minister Theresa May, in theory his closest international ally.

So much for the special relationship.

Image copyright Reuters Image caption Supporters of the far right Britain First group promoted by Donald Trump

It is hard to imagine now that the president's delayed state visit to the UK, scheduled for early next year, can go ahead without howls of outrage from a large section of the British public. Downing Street, desperate for a post-Brexit trade deal with the US, insists that the trip remains on.

It is a far cry from the time that the two nations fought side by side to defeat Nazism.

Sprinkled among the fine and idealistic speeches in my book, like granules of arsenic, are the words of fascists and racists. Nazis Adolf Hitler ("my patience is now at an end") and Reinhard Heydrich ("the final solution"), the British fascist Oswald Mosley ("England again dares to be great"), and, later, the Conservative MP Enoch Powell ("the River Tiber foaming with much blood").

Reading them now, a question comes to mind: did American soldiers fight and die on the beaches of Normandy so their president could promote fascism?

It is an astonishing question, absurd even. To many it may seem offensive even to ask.

But it falls to reporters to describe in plain language what we see, and promotion of fascism and racism is all too easy to observe in the United States of 2017.

Mr Trump amplified the fascism of Britain First, sending its message booming and bouncing around the world. It is a message which continues where Mosley, the leader of the British Union of Fascists, left off. His huge rally at London's Earl's Court in July 1939 was advertised using the slogan Britain First and he uttered it himself in his speech that night, a speech in which he also defended Hitler and attacked the "corrupt interest of Jewish finance".

According to Wikipedia, citing a now deleted web page, today's Britain First aims to protect "British and Christian morality", to preserve "our ancestral ethnic and cultural heritage" and to maintain "the indigenous British people" as the nation's "demographic majority".

Image copyright Getty Images Image caption The Ku Klux Klan has rallied openly on the streets of America this year

Mr Trump insists he wants to put America First for all Americans, regardless of race or religion, but the president's opponents have accused him of using so-called "dog-whistle" politics to appeal to like-minded voters.

The president opened his campaign for the White House by promising to wall off Mexico and create a "deportation force" to expel more than 10 million illegal immigrants from the country.

"When Mexico sends its people, they're not sending their best…they're bringing drugs, they're bringing crime, they're rapists, and some I assume are good people but I speak to border guards and they tell us what we're getting," he said.

He tweeted (and later deleted) false statistics about the percentage of white people killed by black people.

His initial reaction to the murder of Heather Heyer as she protested about a neo-Nazi rally in Charlottesville, Virginia was to insist there was blame "on many sides" and to defend some "very fine people" who marched with the fascists. The comments, which appeared to place the Nazis and their opponents on the same moral plain, left members of his own party reeling in horror.

The former Republican presidential nominee Mitt Romney spoke for many when he tweeted: "No, not the same. One side is racist, bigoted, Nazi. The other opposes racism and bigotry. Morally different universes."

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On Islam too Mr Trump is sharply at odds with his party predecessors, who generally took great care not to link radical extremist ideology with the wider views of a religion followed by nearly a quarter of the world's population, an estimated 1.8bn people.

When, in March 2016, CNN's Anderson Cooper asked Mr Trump whether he thought Islam was at war with the West, the presidential candidate's reply was remarkable.

"I think Islam hates us. There's something there. There's a tremendous hatred there… There is an unbelievable hatred of us," he said. Pressed on the subject, he declined to draw a distinction between mainstream Muslims and jihadists. "It's very hard to separate," he said.

On the campaign trail, Mr Trump called for "a total and complete shutdown of Muslims entering the United States" and he has at least contemplated closing mosques and creating a database of Muslims in the US.

Image copyright Getty Images Image caption Trump takes a call in the Oval Office, alongside then-advisor Steve Bannon (right)

At the end of this century, how will such words sit alongside those from Hoover and Roosevelt, Kennedy and Reagan? Will they look strange or normal? Will the United States again be promoting plurality, or will it be retreating into the supposed security of a white Christian society?

In the past two years I have met many, many Trump supporters who are decent, hard-working Americans with no axe to grind against minorities, but I have also met more than a handful of racists and white supremacists who cheer on the man in Pennsylvania Avenue.

And Mr Trump is championed by the influential new media of the far-right, led by none other than the president's former chief strategist, Steve Bannon of Breitbart.

Mr Trump is far from the first president to diverge from the democratic ideals of the United States, but in doing so as brazenly, as often, and in such a racially and religiously charged manner, he fosters division at home and imperils his country's reputation abroad.

The flame of American idealism, which shone so brightly from my book of speeches, is guttering.