Senator Amy Klobuchar has pulled out of the race to become the Democrat presidential candidate and will back Joe Biden.
She is heading to Dallas and plans to join Mr Biden at his rally there on Monday, her campaign said.
The Minnesota senator is the second person to withdraw in 24 hours after Pete Buttigieg ditched his bidon Sunday night.
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Former vice president under Barack Obama, Joe Biden has seen his campaign rejuvenated after winning the South Carolina primary a few days ago and the support of Ms Kloubchar will be a further boost.
The lawyer and former prosecutor finished third in the New Hampshire primary but struggled to repeat that success.
She was hoping to be the moderate choice for the Democrats but her chance of occupying that role weakened when Mr Biden confirmed he was entering the contest.
The senator had one of the more memorable campaign launches, standing in a Minnesota snowstorm last February to show her “grit” and Midwestern sensibilities.
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Ms Klobuchar’s support for Mr Biden is an attempt to fight off the leading challenge from progressive Democrat candidate, Bernie Sanders.
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Her decision to pull the plug on her campaign comes a day before Super Tuesday – when 14 states vote on their preferred Democratic candidate.
It offers the biggest single haul of the 1,991 delegates needed to win the nomination at its national convention in July, with about 1,357 delegates up for grabs.
The party’s pick will eventually hope to unseat Donald Trump when US voters go the polls on 3 November.