For weeks now it was clear that the Democratic primary was over given former Vice-President Joe Biden's commanding lead in the polls and delegates. Further, the coronavirus situation had basically put a freeze on debates, campaigning, fundraising, and primaries that would allow Sanders to have a chance of making up the deficit.
It was a stunning turnaround from late February in which Sanders was the clear frontrunner. He had essentially tied for first place in Iowa with Mayor Pete Buttigieg, won New Hampshire, and followed up with a decisive victory in Nevada. He had momentum going into South Carolina as he was in second place to Biden.
Further, the moderate vote was divided between Buttigieg, Senator Amy Klobuchar, former NYC Mayor Michael Bloomberg, and Biden which was a different dynamic than the 2016 race. In contrast, Sanders' only competition for the progressive vote was Senator Elizabeth Warren, and he was handily winning that battle.
Turning Point
Prior to the South Carolina primary, Sanders' odds for the nomination was at 65%. The polling indicated a tight race between Biden and Sanders with national polls showing him Sanders in first place and Biden in fourth or fifth place. However, Biden shocked the world by winning South Carolina with 48% of the vote, and Sanders finished in second with 20%.
Biden's momentum continued as other moderates quickly dropped out of the race and endorsed Biden. And, he won the majority of Super Tuesday contests. Prior to South Carolina, Biden's odds of winning the nomination were at 13%. Within a month, they had rocketed up to 90%.
In hindsight, it was clear that Sanders' frontrunner status was more a function of a divided field rather than his appeal to voters. In 2016, he outperformed low expectations and ended up being a strong competitor to Hillary Clinton. He failed to appeal to black voters and performed strongly with rural, white voters.
In 2020, he also failed to win over black voters, largely falling short on electability concerns. He also lost ground among rural, white voters who moved to Biden. Additionally, his base of young voters failed to show up in a meaningful way that would be indicative of a "political revolution" that his candidacy was based on.
Sanders' Lasting Impact
Although Sanders failed to win the nomination, his campaign was successful in moving the Party to the left especially in terms of issues like healthcare, minimum wage, and climate change. He also amassed nearly 2 million volunteers, put together an impressive small-donor fundraising operation, and got millions of young people into politics.
One failure of Hillary Clinton's campaign was to get Sanders' 2016 voters excited about her campaign either through her VP selection or her platform. Based on exit polls, it's estimated that around 15% of Sanders' voters may have voted for Trump or third-party.
For Biden to win, he is going to have to win over Sanders' base. It will certainly be a challenge given his moderate stance, track record in Congress, and ties to the establishment. However, if he can manage this feat, then he becomes the odds-on favorite to defeat President Donald Trump in the upcoming election.