As Donald Trump delivered his first State of the Union address to a divided Congress in January last year, Cory Booker, the junior US senator from New Jersey, sat in the front row.
Jaw clenched, eyes wide and unblinking, he stared directly at the president with undisguised venom. He never looked away once. In fact, Mr Booker looked very much like he wanted to punch Mr Trump.
Two weeks earlier Mr Booker had displayed the same wild-eyed fervour as he excoriated Kirstjen Nielsen, Mr Trump’s homeland security secretary, over the president’s alleged references to "sh–hole countries".
As Ms Nielsen gave evidence to the Senate judiciary committee Mr Booker launched an extended tirade from the bench. The senator had, he said, shed "tears of rage" over Mr Trump’s comments.
I’m running for president. Join me on this journey. https://t.co/fEDqOVIfwh pic.twitter.com/h1FTPUYRzo
— Cory Booker (@CoryBooker) February 1, 2019
Video clips of Mr Booker went straight to the top of the Twitter charts and, while Republicans mocked him for grandstanding, his fame spread further through the social media universe.
If outraged Democrats want a champion in 2020, then the 6ft 4ins Mr Booker – one inch taller than Mr Trump – is clearly a major contender. He said recently: "I am so determined to fight and stop Donald Trump."
On Friday, he declared he would run for president.
There is something of the Spartan about Mr Booker. He seems almost like a boxer preparing for his biggest fight with a single-minded focus on his opponent.
He is 49 and single, teetotal (like Mr Trump) and vegan (not like Mr Trump). He engages in intermittent fasting, a fad diet, which he credits with giving him more energy for the fight.
His office, on the third floor of a building adjacent to Congress, features pictures of Martin Luther King Jr, the abolitionist icon Harriet Tubman, and Mahatma Gandhi.
Mr Booker is one of only three black US senators. He was born in Washington DC and his parents, Cary and Carolyn, were among the first black executives at computer giant IBM.
Underlying all his convictions is an unshakable religious belief which informs everything he does.
Mr Booker grew up Episcopalian – his mother was also a Sunday school teacher – but he went on to become a Baptist.
His academic CV is impeccable – political science at Stanford, a Rhodes scholarship to Oxford, going on to study law at Yale.
At Yale he spent some his spare time offering free legal advice to low-income families. He was also a star American football player at high school and college level.
Even then, there were people who encountered Mr Booker who felt he could become America’s first black president, and it wasn’t long before he started running for office.
In 1998 he caused a local upset by winning a seat on the council in Newark, New Jersey. He then went on a high-profile 10-day hunger strike and lived in a tent to highlight the problems of drug dealing on the streets.
At the time Mr Booker publicly described himself as the "most ambitious person you will ever meet".
Four years later he ran for mayor of Newark, and lost a vicious campaign in which his opponent called him an "Uncle Tom" and claimed Mr Booker’s campaign was being funded by the Ku Klux Klan.
Even though he lost a documentary about the campaign called "Street Fight" made Mr Booker into something of a star.
In 2006 he won, becoming mayor of Newark, where he still lives in a relatively modest home off Martin Luther King Boulevard.
Eight years later, in 2014, he was elected to the US Senate for New Jersey. His term ends in 2020, but he could become president by then.
However, while Mr Booker’s enthusiasm, commitment to public service, intellect, and soaring oratory are not in doubt, there are a umber of questions hanging over his potential candidacy.
Some in the Democratic Party have expressed doubts that he overreaches in his speeches, casting political issues in an abstract fashion that doesn’t resonate with voters.
For example, in speeches he repeatedly talks about his desire to introduce a "conspiracy of love" – his signature phrase and possible election slogan – which has left some listeners confused.
David Axelrod, former adviser to Barack Obama, called him "brilliant" but said Mr Booker has a tendency to "perform" which can make him seem less authentic. Mr Axelrod suggested he "take a few miles an hour off his fastball".
In addition to questions over style there are, perhaps more seriously, others over substance, specifically Mr Booker’s ties to Wall Street and the pharmaceutical industry.
In a Democratic primary campaign he would be expected to get a rough ride from those on the progressive, Bernie Sanders wing of the party.
When he was elected to Congress Mr Booker’s campaign received more donations from the financial sector than any other candidate.
Over the last five years he has received donations of more than $2.6 million from Wall Street, including from hedge funds, and another $2.8 million from lawyers and law firms, according to the Center for Responsive Politics.
In Congress he voted with Republicans against reducing prescription drug prices.
Some of his critics within the Democratic Party have accused him of being "bought and paid for" and "aligning with big money.
Meanwhile, Mr Trump has suggested he would relish a fight with Mr Booker. As neighbours in New York and New Jersey the two men know a lot about each other.
Mr Trump tweeted: "If Cory Booker is the future of the Democratic Party, they have no future! I know more about Cory than he knows about himself."
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