Why Bernie Sanders is struggling to replicate Jeremy Corbyn’s success in taking control of a party

The leadership of the Labour Party was an easier prize for an outsider to win than the Democratic nomination as presidential candidate

Bernie Sanders is not like Jeremy Corbyn after all. Although their political views seem similar, there are important differences. One is that Sanders does not have the same problem with antisemitism. The Jewish Chronicle last week carried a leading article headlined, “Bernie Sanders is no Jew hater, so don’t compare him to Jeremy Corbyn.” The other is that Sanders is a sharper, more aggressive campaigner.

But the real difference is that Sanders is operating in a different political system. Where Corbyn inspired 300,000 people to join the Labour Party to elect and then re-elect him as leader, Sanders faces a much bigger task to be chosen as the Democratic nominee for the presidency.

Sanders inspires a similar enthusiasm among a similar coalition of young idealists and older people who call themselves socialists. “Socialist” has a different meaning in the US, but it’s similar to the way Corbyn supporters use it here to distinguish it from the milk-and-water Labour politics of the Ed Miliband interregnum. But mobilising those supporters is harder in the US system.

Sanders did well enough in Iowa, where the caucuses give the vote only to the highly motivated, who have to turn up for a party meeting. Pete Buttigieg, who is almost local to Iowa, also did well, but Joe Biden did badly.

But primary elections are a different matter. In most states they are open to all voters, and, although an enthusiastic minority is important, especially in providing campaign workers, it cannot guarantee the votes. Sanders did well in New Hampshire, which is next door to Vermont, his home state, but elsewhere he has struggled against Biden, a candidate with a wider appeal among the general electorate.

After Biden did better than expected in South Carolina at the weekend, he has now repeated the trick on a larger scale in the Super Tuesday states. Sanders will still pick up a lot of delegates in California, but in most other states, including Texas, Biden is winning more.

That means Biden is suddenly on course to win the nomination. The votes are still being counted, but my benchmark is Nate Silver’s forecast model. Last night, before the Super Tuesday results started coming in, it suggested Sanders was heading to win just one third of the delegates to the Democratic convention. Given that Biden did better than expected, that figure will have fallen.

It is not over yet: even when yesterday’s votes are all counted, more than half of the delegates still have to be chosen, but Sanders now needs something dramatic to change the course of the race. Biden has shown that in elections open to all voters in Middle America states, he is bulldozing his way to victory. Only in liberal states such as California, Colorado and Utah is Sanders able to hold out.

Of course, Jeremy Corbyn did well in a general election in Britain, cutting the Conservative lead in vote share to just two percentage points and depriving Theresa May of her majority in parliament in 2017. But we can now see how many special factors applied to that election. May was expected to win, but fought a poor campaign and the voters wanted to limit her power.

And US opinion polls suggest that, if Sanders were to face Donald Trump in the general election in November, he would do well – although on average Biden comes out slightly better.

But in the US system, Sanders has to beat Biden first, and that seems to be the hurdle he cannot get over. However ill-defined the term “socialism” is, it seems that enough middle Americans don’t like it. It seems that, after all, they prefer the mainstream, blue-collar Democratic party values embodied by Barack Obama’s vice president.