Bernie Sanders is on course to lose the 2020 Democratic nomination, and there are a whole host of reasons that’s true. I and many others have spotlighted the senator from Vermont’s inability to expand his appeal beyond young voters and to black voters. He seems to have run into a hard ceiling yet again, and in a two-person race, that spells doom — barring some extraordinary shifting in the weeks ahead.

But one big reason Sanders is losing has gotten short-shrifted: the switch from caucuses to primaries.

The vast majority of states that held caucuses in 2016 moved to primaries this year. Sanders won many of them by very wide margins four years ago, thanks to smaller, more passionate electorates and an organized delegate effort. Now that those states are holding primaries, Sanders is bleeding delegates in them — badly.

It happened last week in Minnesota, where Sanders won by 24 points in its 2016 caucuses but lost by nine to former vice president Joe Biden. In Utah, Sanders won the 2016 caucuses by 59 points but carried its 2020 primary by just 17. (The one state where he just about matched his 2016 caucus performance was in Colorado).

And it happened again Tuesday. Sanders’s 57-point win in Idaho became a six-point deficit. And his 46-point win in Washington state is now effectively a draw, with a winner still undeclared.

All told, in these five states, Sanders has shed an average of 38 points off his 2016 margins. By contrast, in all the states that kept their caucus or primary format between 2016 and 2020, he’s less than 3 points off his 2016 margins — running close to the same.

The tale is told even more succinctly in delegates. In the five states that shifted from caucuses to primaries, Sanders ran up a big win in pledged delegates, thanks to those huge margins — 206 for him and 94 for Hillary Clinton, a margin of 112 delegates. As things stand right now, he’s gaining fewer than 10 delegates in them.

And what is Sanders’s current delegate deficit? According to the latest Washington Post count, he trails Biden by 143 delegates. In other words, if he had been able to rack up the kind of delegate margins in just these five states that he did in 2016, the race would be very, very close.

Whether he would actually have been able to do so is impossible to say. In the states that stuck with caucuses this time — Iowa, Nevada and North Dakota are the ones that have voted thus far — Sanders is running about even to where he did in 2016. But only in North Dakota did he win — and win by a large margin back in 2016. And in that state, his margin shrank from 38 points in 2016 to 13 points on Tuesday. It’s entirely possible he wouldn’t have been able to emulate the huge delegate hauls he got in states like Utah, Idaho, Washington state and Minnesota, where Sen. Amy Klobuchar’s late exit helped flip the state to Biden.

But it’s clearly something that has hurt Sanders. For all the talk about whether the process was “rigged” against him in 2016 and might be rigged against him again in 2020, it might be this procedural change that looms as large as anything. Sanders supporters pushed for stopping superdelegates from deciding the nomination on the first ballot at the convention, but the shift away from caucuses is a big reason we don’t have more of a contest right now.