It seemed like a harmless question, but when you’re the 44th President of the United States there’s no such thing. On Tuesday afternoon, Barack Obama turned up at the second annual Kids’ State Dinner, hosted by his wife, Michelle, and attended by the winners of her competition to create a healthy lunchtime recipe. One of the 54 children at the event asked the President to name his favourite food, to which he replied, implausibly: broccoli. Given his grasp of political history, Mr Obama must surely have known that broccoli was a hot potato.

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Like pasta and organised crime, broccoli was popularised in America by the Italians. Brothers Stephano and Andrea D’Arrigo were the first to cultivate vast crops of the divisive brassica from their farm in San Jose, California during the 1920s – just in time to grace the lunch table of a young George HW Bush. In 1990, Mr Bush famously banned broccoli from Air Force One, explaining, “I do not like broccoli... And I haven’t liked it since I was a little kid and my mother made me eat it. And I’m President of the United States, and I’m not going to eat any more broccoli!”

California broccoli farmers were outraged, and delivered a reported 10 tons of their product to the White House in protest. The vegetables were donated to local homeless shelters. During her husband’s campaign to unseat Mr Bush, Hillary Clinton was photographed holding a sign that read, “Let’s put broccoli in the White House again.” It’s commonly held that “the economy, stupid,” won Bill Clinton the 1992 election – but was it really the broccoli?

More than 10 years after his father’s gaffe, George W Bush almost caused a diplomatic incident with his own dislike of the Democrats’ favourite vegetable. On an official visit to Mexico in 2001, he stopped in at then-Mexican President Vicente Fox’s San Cristobal ranch, which sits adjacent to a large field of broccoli. When reporters asked his opinion on the crop, Dubya gave it the thumbs-down, saying: “Make it cauliflower.” It is not clear whether he knew at the time that Fox’s family owned a substantial broccoli farm.

Last year, broccoli again hit the headlines, as a symbol of President Obama’s controversial healthcare reforms. During a debate about Obamacare in the Supreme Court, Justice Antonin Scalia suggested the Government’s new requirement that everyone purchase health insurance could open the door to grocery-store tyranny, by forcing everyone to purchase healthy food, too. “Everybody has to buy food sooner or later,” Scalia said. “Therefore, you can make people buy broccoli.”

The first known use of the healthcare/broccoli analogy was in 2009, when the editor of CNS News asked in an op-ed, “Can President Barack Obama and Congress enact legislation that orders Americans to buy broccoli?” The answer, the Supreme Court decided, was ‘No’. In the majority opinion approving the Affordable Care Act, Chief Justice John Roberts made special mention of broccoli. Were Congress to force consumers to eat healthy foods, in order to reduce obesity and thus curb the costs of Obamacare, Roberts wrote that it would be a dangerous use of government power, and go against the laws and traditions of the US.

Around 90 per cent of the country’s broccoli is grown in California, where the mix of warmth and fog suits the anti-carcinogenic crop down to the ground. Washington’s disdain for the vegetable may stem, therefore, from its lack of freshness – most broccoli on DC dinner plates will already have suffered several days in trucks and warehouses. Still, America is learning to love broccoli: US broccoli farming and sales of fresh broccoli have both increased substantially since the first Bush presidency.

Mr Obama himself is a recent convert. During the 2012 presidential election, his favourite foods were said to be the somewhat less healthy chilli, chips and pork chops. In an interview last year, he also admitted a weakness for nachos. “If I get nachos and guacamole I can go to town on that stuff,” he said. “I asked my team to restrict my intake. If they put it in front of me it’s gone.”

So what swayed him to broccoli: Mrs Obama’s healthy eating advocacy, the White House chefs, or simply a national trend towards fresher, better prepared veg? “My family when they cooked vegetables, they would just boil them and they’d get all soft and mushy,” Obama told his audience at the Kids’ State Dinner. “Nobody wanted to eat a pea or a Brussels sprout because they’d be all mushy… But now I actually like vegetables, because they’re prepared right.”

Power broccoli: For and against

Thomas Jefferson

The third president of the US may well have been its first broccoli enthusiast. He imported seeds from Italy to plant on his estate at Monticello in 1767.

George H W Bush

The elder Bush, the 41st US president, was fiercely anti-broccoli, banning it from Airforce One. “I do not like broccoli,” he said in 1990, “and I haven’t liked it since I was a little kid... I’m the President of the United States, and I’m not going to eat any more broccoli.”

Hillary Clinton and Tipper Gore

The wives of the future president and vice-president headed a “Let’s put broccoli in the White House again” campaign in 1992.

Silvio Berlusconi

The former prime minister and bunga-bunga enthusiast is one of several broccoli fans in Italian politics.

George W Bush

Gave a “thumbs down” to the broccoli of President Vicente Fox during a presidential visit to Mexico in 2001.

Barack & Michelle Obama