Former vice president Joe Biden has become the presumptive democratic nominee for president after Vermont senator Bernie Sanders, the last major opponent still vying for the democratic nomination, ended his campaign. Despite becoming the victor of the nomination contest and going into the general election with president Donald Trump presiding over one of the largest stock market crashes in American history, Biden cannot win the presidency.

There are numerous reasons why Biden will not win the presidency, but the primary issue is too many democratic voters have become disillusioned with the party. A significant number of Sanders supporters in the media have already declared that they will not vote for Biden. Large swathes of voters are also pledging not to vote for Biden as well.

In 2016, one of the big ways the party attempted to get out voter turnout was repeating that a vote for anyone but Clinton was a vote for Trump, and media figures are already repeating this same rhetoric again. In 2016, it got a large portion of Sanders supporters to vote for Clinton, but Sanders supporters are coming around to the view that the only way to move the party remotely left to where they stand is to show they will withhold their vote if the party doesn’t shift. Unless the Biden team makes major concessions, then many progressive voters, a large and required constituency to win, will withhold their vote.

There are some things Biden can do to attempt and win this vital base. First, he can pick a progressive vice president. Massachusetts senator Elizabeth Warren would not be a good pick because Sanders supporters became disillusioned with her after she refused to drop out before super Tuesday, but there are other options like former Ohio state senator Nina Turner who is extremely liked among progressives.

The other thing Biden can do is make major concessions. Small concessions, like changing the medicare age, will not do remotely enough to win the progressives who are tired of being shamed into voting for the better of two evils every election cycle. Biden would need to change his policies enough to not be a nevil, including endorsing a public option and making public colleges and universities tuition free.

If Biden doesn’t make concessions to progressives, then he is set to lose the vital progressive base. While not the entirety of the democratic party, the progressive block is more than large enough to tank any democrat’s campaign if most of their votes are withheld. This is what happened when former president Theodore Roosevelt ran as a third party candidate, and split the liberal voters in the 2012 election, and it will happen again as progressives pledge to vote for third party candidates.