A couple of weeks ago, it looked like Michael Bloomberg might be the candidate that would challenge Bernie Sanders. He had spent half a billion dollars on advertising, and was looking pretty good in the polls in several states. He (and many political pundits) expected him to win enough delegates on Super Tuesday to put him among the frontrunners.
That didn't happen. When Biden scored a huge win in South Carolina, voters began to take another look at him. And by Super Tuesday enough of them had jumped on his bandwagon to give him a huge Super Tuesday victory -- winning 10 of the 14 states (including some that most thought Sanders was sure to win).
Bloomberg won only 24 delegates out of the more than 1300 delegates available -- far less than he had hoped for, and far behind Biden and Sanders.
Bowing to reality, on Wednesday Bloomberg suspended his presidential campaign. He then endorsed Joe Biden, and promised to use his campaign organization (and money) to help Biden win the nomination and defeat Trump.
Bloomberg told his supporters, "I entered the race for president to defeat Donald Trump, and today, I am leaving the race for the same reason: to defeat Donald Trump".
This leaves three people in the race -- Joe Biden, Bernie Sanders, and Elizabeth Warren (Tulsi Gabbard is also running, but no one is voting for her).