Pete Buttigieg exited the 2020 Democrat presidential race, ending an unlikely bid that saw a gay small-town mayor overpower governors and senators in the fight for the party nomination.

"Today is a moment of truth," Buttigieg said from South Bend, Indiana, where he served as mayor for two terms. "The truth is the path has narrowed to a close, for our candidacy, if not for our cause."

Buttigieg said he had a responsibility for considering "the effect of remaining in this race any further."

"Our goal has always been to help unify Americans to help defeat Donald Trump and to win the era for our values. And so 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 our country together," he said.

The remarks, punctuated with chants of "2024!" from supporters, concluded with no endorsement from the 38-year-old moderate.

His decision to drop out of the race came a day after former Vice President Joe Biden won a crushing victory in the South Carolina primary, reenergizing a campaign that had flagged in the first three nominating contests in Iowa, New Hampshire and Nevada.

Biden's renewed momentum would make it difficult for Buttigieg to win over moderate voters in this week's Super Tuesday. It also caused some financing trouble: In the wake of Biden's victory, bundlers working for his campaign were able to lure some donors who had been backing Buttigieg, CNBC reported.

During his longshot bid, Buttigieg outperformed expectations, assembling what at points was a substantial war chest and building out a vast national operation. Buttigieg, the first openly gay major presidential contender, scored a narrow delegate edge over Sen. Bernie Sanders in the Iowa caucuses and finished a strong second in New Hampshire's primary.

But the one-time candidate for chair of the Democratic National Committee ultimately failed to sustain his campaign's momentum and ran into difficulty attracting the support of black and other minority voters.

This became clear in the Nevada caucuses, where he finished a distant third place with only 2% of the black vote, and in South Carolina, where he collected 3% of the black vote and finished in fourth.

Buttigieg had predicted that wins in Iowa and New Hampshire would boost his support in the more diverse states that followed, but that outcome did not materialize.

Buttigieg's showings in Nevada and South Carolina muddied potential paths to victory for the millennial Afghanistan war veteran ahead of Super Tuesday, when 14 states will host contests that collectively award a third of the race's total delegates.

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Earlier on Sunday, on NBC's "Meet the Press," host Chuck Todd pressed Buttigieg about his decision to stay in the race.

"Every day we are in this campaign 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," Buttigieg said.

The Super Tuesday contests have escalated pressure on candidates who are underperforming in state surveys to drop out.

Massachusetts Sen. Elizabeth Warren and Minnesota Sen. Amy Klobuchar have resisted those calls, though.

Warren's campaign released a memo on Sunday describing the Democratic National Convention in July as the "final play" for the campaign and committing to fight for delegates for as long as it could until then.

An aide to Klobuchar told CNBC shortly after Buttigieg's departure from the race became known that the moderate senator was not planning to drop out any time soon. Klobuchar was attending an event in her home state Sunday evening. Minnesota is among the Super Tuesday states.

-- CNBC's Lauren Hirsch contributed to this report.