Joe Biden’s surge poses threat to Bernie Sanders’ US primary hopes

Presidential candidate Joe Biden’s surprise sweep of Super Tuesday primary contests was driven by voters who only decided on their preferred candidate in the US Democratic race the week before, suggests an FT analysis of exit polls from the March 3 votes.

While his main rival Bernie Sanders’ supporters are steadfast — many made up their mind they would vote for him well before February’s primaries — there is little evidence that he is attracting new voters in significant numbers. This lack of momentum may prove decisive in scuttling his campaign. 

As other moderate candidates dropped out of the race, 19 per cent of moderate voters were up for grabs in the final days before Super Tuesday. Mr Biden succeeded in getting many to cast their primary ballots for him. 

The late surge of votes for Mr Biden was apparent across all 14 states voting in last week’s primaries, including Bernie Sanders’ home state of Vermont. Although Mr Sanders won the state, Mr Biden beat his rival when it came to attracting votes from those who only chose their preferred candidate in the last week.

The analysis suggests that the South Carolina primary on February 29, which the former vice-president won, was pivotal in providing the fresh appeal to voters across the country, reviving his previously stuttering campaign. 

Mr Biden’s Super Tuesday resurgence is reminiscent of the boost that propelled former president Barack Obama to victory ahead of Hillary Clinton in 2008. Mr Obama received an initial nine-point boost in his polling after winning the opening Iowa caucuses. Like Mr Biden, he then won South Carolina ahead of a strong showing on Super Tuesday, allowing him to overtake the early frontrunner.

The exit polls from Super Tuesday’s primaries also show that Mr Sanders has remained most popular with younger voters and those who had not voted before, while Mr Biden appealed to older voters.

Mr Sanders has maintained his support from Hispanic and Asian voters, while Mr Biden's support among black voters was equally apparent. However, the impact of Sanders’ core voter base was reduced by low turnout among young people. 

The 65-plus age group that heavily favoured Mr Biden over Mr Sanders makes up only 19 per cent of the Super Tuesday electorate, but accounted for 44 per cent of votes cast.

Mr Biden has also benefited from the withdrawal of other candidates, freeing up moderate votes.

Ahead of the South Carolina primary, supporters of both Pete Buttigieg and Amy Klobuchar said they were more likely to vote for Mr Sanders than Mr Biden if their candidate dropped out. After Mr Biden’s emphatic victory on February 29, however, both candidates left the race and endorsed Mr Biden. 

Among Super Tuesday voters who decided who to vote for in February, 15 per cent opted for either Mr Buttigieg or Ms Klobuchar, but among those who decided in the final days leading up to the vote, only 4 per cent stuck with the pair.

Former New York City mayor Michael Bloomberg was the wild card in the Democratic race. Following the billionaire’s poor performance on the debate stage on February 19, however, his share of the Super Tuesday vote declined from 20 per cent among early deciders to 12 per cent among late movers. 

Mr Sanders now needs to find a way of quickly reversing the swing towards his rival in what has now become a two-horse race — and endorsements may not help clear the way for him. A post-Super Tuesday Reuters/Ipsos poll suggests that voters who previously supported the progressive candidate Elizabeth Warren are no more likely to turn to fellow progressive Mr Sanders than they are to Mr Biden.

Instead, Mr Sanders will need greater turnout from younger, Hispanic and Asian voters than there was on Super Tuesday. But demographic data for the states in the next round of democratic primaries — Mississippi, North Dakota, Michigan, Idaho, Missouri and Washington — suggest there will probably be limited opportunities for this.

Hispanic voters make up no more than 8 per cent of the citizen voting-age population in this week’s primary states.

There is still a long way to go in the race to cross the threshold of 1,991 pledged delegates needed to secure the nomination at the Democratic Convention in July. But Mr Sanders has a long battle ahead of him if he hopes to beat Mr Biden’s surge.