Image copyright Reuters

US Democratic presidential candidate Cory Booker has announced he is ending his campaign after disappointing poll numbers.

The African-American New Jersey senator had failed to qualify for the Democratic debate on Tuesday in Iowa.

The former rising star's message of unity at a time of deeply divided politics failed to win over voters in the crowded 2020 field.

There are now 12 Democrats remaining in the race for the White House.

"Today I'm suspending my campaign for president with the same spirit with which it began," Mr Booker said in a video announcing the end of his campaign.

In an email to supporters he said: "I'm proud of the ideas we brought to this Democratic primary and, more importantly, the values we championed throughout - that the only way we make progress is by bringing people together - even when we were told that our approach couldn't win."

Mr Booker, 50, had focused his campaign on a message of "love and unity" to combat what he depicted as Mr Trump's divisive rhetoric.

But his prescriptions for criminal justice reform, as well as reducing economic and racial inequality failed to resonate with voters.

The former Mayor of Newark, New Jersey, had polled an average of 2% nationally, according to RealClearPolitics data.

Front-runners Joe Biden and Bernie Sanders have been polling at 29% and 20% on average respectively.

Mr Booker was unable to match his competitors in fundraising. Politico reported he pulled in only $6m (£4.6m) in the final quarter of last year, far less than his top-tier rivals.

Unhappy ending for 'happy warrior'

If political success came from the strength of a stump speech, Cory Booker would be on the way to the Democratic nomination. He was simply electric in small crowds, hosting events that were part political rally and part religious tent revival.

Many popular candidates receive standing ovations when they begin a speech. Booker would regularly get them as he concluded - even from non-supporters.

Especially, it seems, from non-supporters. That was the rub.

Democrats tended to like Booker. Very few, however, told pollsters they would vote for him. Even fewer were interested in donating to his campaign.

Booker consistently received plaudits for his skillful "happy warrior" debate stage performance. Without the requisite support, however, those debate invites dried up months ago.

Some Democrats clearly wanted a warrior with a sharper edge and backed someone else. Those who sought an upbeat candidate have supported Joe Biden or Pete Buttigieg - the younger, less experienced Rhodes scholar and former mayor in the race.

That left Booker with no clear base of support - and it cost him. Booker's campaign had a lot of potential on paper. His career is far from over, but least for now, that's where his potential will remain.

Meanwhile, with Booker's exit, there are 12 candidates still in the race. In a party that celebrates its diversity, all but three are white - none of whom will be on debate stage tomorrow night.

That is a challenge the party will have to confront in the days ahead.

Last week, Mr Booker said the impending presidential impeachment trial could deal a "big, big blow" to his campaign as he would be off the trail for weeks.

On 9 January, he told the Associated Press: "If we can't raise more money in this final stretch, we won't be able to do the things that other campaigns with more money can do to show presence."

Fellow Democratic contender Marianne Williamson quit the race at the weekend, while Julian Castro, who was the only Latino in the field, dropped out of the race earlier this month.

Mr Booker, who launched his campaign on the first day of Black History Month in February last year, had recently complained about the lack of diversity in the Democratic presidential field.

He told MSNBC in December: "We're spiralling towards a debate stage that potentially could have six people with no diversity whatsoever."

Just as he predicted, all six Democratic White House hopefuls who will take to the stage for a televised debate on Tuesday in Iowa are white; two are women.

Most of the remaining Democratic candidates are male and white, which is provoking criticism for a party that prides itself on multiculturalism.

Of the remaining contenders, only Andrew Yang, Deval Patrick and Tulsi Gabbard are not white.

The Washington Post recently ran a column saying that the Democrats "are starting to look like a 'Whites only' party".

Mr Booker had also struggled to attract black voters, many of whom favoured Mr Biden, Mr Sanders or Ms Warren in early opinion polls.

President Donald Trump weighed in soon after Mr Booker's announcement, saying: "I was sooo concerned that I would someday have to go head to head with him!"

Mr Booker's 2020 rivals have also responded to his exit.

Minnesota Senator Amy Klobuchar said she would miss him on the campaign trail, and Mr Biden said he had campaigned with "joy and heart".

Mr Yang, calling Mr Booker a friend and brother, said "the fight continues".

Fans of the New Jersey senator's girlfriend, actress Rosario Dawson, mourned what might have been had she become first lady of the US.

Mr Booker had a quip ready.

Image copyright Getty Images Image caption Mr Booker and Ms Dawson have been dating for just over a year

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