Former Democratic candidate Amy Klobuchar endorses Joe Biden

Former rivals Pete Buttigieg and Amy Klobuchar endorsed Joe Biden's presidential candidacy on Monday (March 2) on the eve of Super Tuesday voting, as moderate Democrats rallied around the former Vice President to strengthen his challenge to front-runner Bernie Sanders.

Buttigieg threw his support to Biden at an emotional appearance at a Dallas restaurant, while Klobuchar delivered a barnstorm of a speech at a rally, reminiscent of the types politicians give at their party conventions when anointing their presidential nominees.

Former U.S. Representative Beto O'Rourke, another former candidate for the Democratic nomination, also endorsed Biden, appearing to cheers as a surprise guest at the rally in Dallas.

Biden is fresh off a resounding victory in Saturday's South Carolina primary and is aiming for a strong showing on Super Tuesday against Sanders, a self-described democratic socialist, who many centrist Democrats fear cannot win against Republican President Donald Trump in November.

But Biden still faces a challenge from billionaire former New York Mayor Michael Bloomberg among voters hoping the party will nominate a moderate to face Trump.