There is a simple explanation for why Sen. Bernie Sanders, who officially suspended his presidential campaign on Wednesday, lost the Democratic nomination: Former Vice President Joe Biden trounced the Vermont senator when the race narrowed to a one-on-one contest after Super Tuesday. The results of the caucuses and primaries before and on Super Tuesday left Sanders trailing Biden by 83 pledged delegates — a significant, but perhaps not insurmountable, deficit. But the Vermont senator lost eight of the 11 contests after Super Tuesday, winning only North Dakota, the Northern Mariana Islands and among Democrats who are American citizens but living abroad. Moreover, many of Biden’s wins were blowouts, ballooning his pledged delegate lead to 311, a margin that is essentially insurmountable.

Of course, the simple explanation for Sanders’s loss begs a deeper question: Why did Sanders do so badly in a one-on-one contest against Biden? I’d offer three explanations, none of which are mutually exclusive from the other two.

Sanders didn’t run a smart enough campaign

In 2016, Sanders built a passionate bloc of supporters who crowded his rallies and flooded his campaign with money, but lost to former Secretary of State Hillary Clinton, a more centrist, establishment Democrat who had greater appeal among black, Southern and older voters. In 2020, Sanders built a passionate bloc of supporters who crowded his rallies and flooded his campaign with money but lost to Biden, a more centrist, establishment Democrat who had greater appeal among black, Southern and older voters. Sanders got almost no backing from elected Democrats in 2016, and didn’t court the party establishment that much in 2020 either. That was a major barrier to his candidacy — not only did Sanders again get little support from the party elite, but that same elite was instrumental in helping Biden consolidate the field and winnow the race to a two-man contest.

Both Clinton and Biden were strong opponents, each having deep connections to a recent Democratic president. But it’s fair to criticize Sanders for losing in 2020 in a fairly similar way to 2016.

By all indications, Sanders and his team did make some attempts to avoid the pitfalls of his 2016 run. It’s hard to measure this, but it seems like Sanders’s outreach to black voters in 2020 was more extensive than four years ago, even if it didn’t bear much fruit. But Sanders’s failure to expand his coalition to older voters, minorities and establishment Democrats all but doomed his campaign.

Sanders and his aides also made new mistakes in 2020. There were some clear indications that some of Sanders’s success in 2016 — among white voters without college degrees, in particular — had more to do with anti-Clinton sentiment than strong support for Sanders. But the senator’s advisers seemed to think that Sanders had a unique appeal to white working-class voters that would simply continue in 2020. So the Sanders campaign decided to invest heavily in the March 10 primary in Michigan, a state packed with white voters without a college degree. Biden not only won Michigan easily, but he won overall among white voters without a college degree (and pretty comfortably).

Sanders stayed in the race for about a month after Michigan, but that loss was really the end of his campaign. It undermined one of Sanders’s central arguments — that his brand of politics appealed to white voters without a degree in a way that the more centrist vision of Biden and Clinton did not, making the Vermont senator a stronger candidate than Biden in the general election.

Sanders and his team also expected that he would boost turnout among younger voters. This did not pan out.

Sanders is clearly a skilled politician — he was probably a few breaks away from winning the nomination in a crowded field that included some formidable figures. But former President Barack Obama (in 2008 against Hillary Clinton) and President Trump (in 2016 against former Florida Gov. Jeb Bush) were able to defeat primary rivals who entered the race with strong political pedigrees. Sanders fell short.

Democrats were wary of a very liberal nominee

We made this case in more detail in an article earlier this week, arguing that Sanders, Sen. Elizabeth Warren and the Democratic left were always going to face an uphill climb in the 2020 primary. Democrats’ overriding priority in 2020 has been defeating Trump, and many in the party view left-leaning ideas as something that makes it harder to win over swing voters. The boomlets around former Rep. Beto O’Rourke and former South Bend, Indiana, Mayor Pete Buttigieg, neither of whom had the traditional qualifications for a presidential nominee, had the feeling of the Democratic Party desperately searching for a white, male, centrist-y candidate to take on Trump. The party landing on Biden (white male, centrist-y) fits that general narrative.

In this view, any mistakes that the Sanders campaign made likely played a trivial role compared to the core elements of his political persona, such as identifying as a democratic socialist and favoring fairly left-wing ideas like Medicare for All. Maybe Democrats would have taken a chance on someone like Sanders at another time, but not with the specter of another four years of Trump if the party’s nominee loses in November.

“If Sanders had this well-organized of a supporter base in 2016, he might well have won,” David Karpf, a professor at George Washington University who specializes in political communication and media, told me. “2016 was defined by deciding the future of the party in power. 2020 was defined by trying to remove the party in power. Those are just completely different dynamics.”

Trump aside, Sanders was always a weird fit as the Democratic nominee

Sanders has finished in second place in the Democratic nomination process the past two cycles. But it’s worth asking: Was Sanders, a white male democratic socialist in his 70s who is not officially a Democrat, really the second-most likely candidate to win the nomination in either 2016 or 2020? Clinton was a strong front-runner in 2016 and basically cleared the field. If she had opted against running in 2016, it’s fairly likely that other prominent Democrats — say, Sen. Amy Klobuchar, Biden or Warren — would have run, and it’s not clear that Sanders could have defeated them either.

The way the primary process played out, with Sanders the clear front-runner after the Nevada caucuses and Biden needing a surprising comeback to win, suggests that Sanders could have won in 2020. But it would have been somewhat fluky if a candidate (Biden) who led in the polls for basically the entire race crashed without the party’s establishment able to mobilize behind any alternative. Had Biden not run in 2020 or faltered fairly early, could Buttigieg, O’Rourke, Sens. Cory Booker or Kamala Harris, or even Warren have defeated the Vermont senator in the same way Biden did, by getting into a one-on-one race with Sanders, running to his right and receiving the bulk of support from the party’s establishment? That seems entirely possible.

Sanders being an older white man is probably relevant here too. In 2016, Democrats opted for a historic choice in nominating a female candidate. In 2020, they nominated a centrist white guy who they believe is the most electable candidate. It’s hard to imagine Democrats in 2016 blocking the first-ever female major-party nominee in favor of a white socialist man — or in 2020 for them to choose a white socialist man over a white centrist man.

In other words, even though a Sanders win seemed plausible and even likely after Nevada, are we really surprised that Sanders is not the Democratic nominee? In the context of modern presidential primaries, the real surprise would have been if Democrats had chosen Sanders over a slew of other candidates running on either Bill Clinton-style electoral centrism (Montana Gov. Steve Bullock, Biden, Klobuchar) or Obama-style hope and change (Booker, Buttigieg, Harris, O’Rourke). Sanders has pushed the Democratic Party to the left on policy and ideology — but now the party has pushed him back to the U.S. Capitol.