Former mayor of South Bend, Indiana, leaves the race to take on Donald Trump after a poor showing in the South Carolina primary

Pete Buttigieg has ended his campaign for the Democratic presidential nomination with a call for Democrats to unite in their fight to beat Donald Trump in the election.

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The 38-year-old former mayor of South Bend has never held statewide or national office but made a strong run in the Democratic primary, winning the Iowa caucuses narrowly from Bernie Sanders, now the national frontrunner, to whom he placed second in New Hampshire.

But Buttigieg could not make progress in Nevada and South Carolina, the first two states with influential minority voting blocs.

Speaking to supporters in South Bend on Sunday night, Buttigieg issued a call for unity. “Today is a moment of truth ... the truth is that the path has narrowed to a close for our candidacy if not for our cause.” he said.

“We must recognize that at this point in the race, the best way to keep faith with those goals and ideals is to step aside and help bring our party and country together.”

“Our goal has always been to unify Americans to help defeat Donald Trump and to win the era for our values.”

Joe Biden, the former vice-president, won the South Carolina primary on Saturday by a landslide margin. The next date on the calendar is Super Tuesday, 3 March, when 14 states, American Samoa and Democrats who live overseas will vote.

Biden will look to harvest support from Buttigieg as he seeks to establish himself as the moderate choice to deny Sanders. The progressive from Vermont, a self-proclaimed democratic socialist, sits in the Senate as an independent. Party figures fear he will not be able to beat Donald Trump in November.

Speaking to CNN on Sunday morning, Biden said he had not had any conversations with other candidates about whether they should drop out and back him but added: “I think everyone knows it’s going to be much more difficult to win back the Senate and keep control of the House if Bernie’s at the top of the ticket.”

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The Minnesota senator Amy Klobuchar is still in the race and is unlikely to quit before her state votes on Tuesday. The billionaire former New York mayor Mike Bloomberg is also a centrist candidate for the nomination but he is self-funding his campaign and has not yet entered a primary.

Another billionaire moderate, Tom Steyer, dropped out on Saturday night.

At first on Sunday, which Buttigieg began with breakfast with former president Jimmy Carter in Plains, Georgia, it did not seem he would take the final step.

“Every day we are in this campaign,” he told NBC News, “is a day that we have reached the conclusion that pushing forward is the best thing we can do for the country and for the party.”

But later in the day he was out.

CNN reported that the former mayor was “unwilling to be [the] reason Sanders is able to get ‘insurmountable’ delegate lead on Super Tuesday”. It was also reported that Buttigieg was not planning to endorse another candidate on Sunday.

Sanders responded to Buttigieg’s exit from the campaign on Sunday night with an appeal to his supporters.

Bernie Sanders (@BernieSanders) I want to congratulate @PeteButtigieg for running a strong and historic campaign, and to welcome all of his supporters into our movement. I urge them to join us in the fight for real change in this country.

Rick Wilson, a former Republican consultant turned anti-Trump organiser who advocates a moderate choice of Democratic nominee, wrote on Twitter: “It’s hard to pick the right time to go in a campaign, but Pete Buttigieg did.”

It seems likely Buttigieg will remain a figure on the national stage. A charismatic campaigner in the centre lane of the primary, having prepared his ground with a run for party chair in 2016, he built an impressive fundraising operation.

He was also the first openly gay candidate for American president.

“The Pete Buttigieg story isn’t over. It’s just beginning,” said Democratic strategist David Axelrod. “He’s 38 years old. He’s vaulted himself into the national conversation.”

“He obviously has work to do on some things that – some weaknesses we’ve seen in this election – but whenever there is a conversation again about Democratic candidates, he’ll be in that conversation. And that’s a remarkable achievement, given where he started a year ago.”

Recently, when the rightwing shock jock and Trump ally Rush Limbaugh questioned whether Americans were ready to vote for a gay president, even the controversialist in the Oval Office was quick to disown the suggestion. On the campaign trail, where he regularly appeared with his husband Chasten, Buttigieg hit back hard.

In comments distributed to the media on Sunday, a Buttigieg campaign official said: “Pete was willing to go where no other candidates were – and when he held a Fox News town hall and got a standing ovation, people realised that Pete’s message of moving past our divided politics was truly possible.”

One of Buttigieg’s last tweets as a candidate linked to a Michigan ballot initiative on anti-discrimination law and promised supporters that as president he would “help pass the Equality Act, and with your courage and activism … create a community where we all belong”.

In a statement, Sarah Kate Ellis, president and chief executive of the Glaad advocacy group, said Buttigieg “showed the world that Americans are ready to accept and embrace qualified LGBTQ public leaders.”

Charles Kaiser, a Guardian contributor and the author of The Gay Metropolis: the Landmark History of Gay Life in America, said: “Even though he is leaving the race, his success in Iowa and New Hampshire was transformative.

“Before Pete Buttigieg no one knew if an openly gay or lesbian American could be a credible candidate for president. Now, no one from the LGBTQ community will ever grow up thinking their sexuality is an unsurmountable obstacle on the road to the White House.”