In the week leading up to France's elections, Prime Minister Theresa May has ordered a snap general election for June 8 in Britain.

May is out to neutralise a few problems. First of all, the Crown Prosecution Service is looking at prosecutions affecting two dozen Conservative MPs. That number is greater than her parliamentary majority of 17. Second, May's administration is hamstrung by its weak majority, as witnessed in a recent U-turn over an attempt to raise taxes for the self-employed. Above all, May is out to finish the left-wing opposition leader, Jeremy Corbyn.

Indeed, the election looks dire for Corbyn, currently at 25 percent in the polls. But why does it seem so much worse than that of France's radical left presidential candidate, Jean-Luc Mélenchon, on 19 percent? Why is Melenchon a threat, while Corbyn looks threatened?

The first part of the answer is that Corbyn doesn't lead a radical split off from social democracy, as Melenchon does. While the latter leads a politically and ideologically coherent organisation, with plenty of media savvy, Corbyn leads a traditional social democratic party.

This didn't happen because of overweening left-wing power, but because of the exhaustion of the old party elites, part of a wider social democratic decline. Those elites never adjusted to the new reality, and Corbyn had no choice but to work with them. They are now stuck with each other, neither willing to give up Labour, and neither able to claim complete control.

This gave Corbyn certain advantages, such as the support of long-entrenched institutions with money and influence, such as the trade unions. He leads not a radical fringe party but the official opposition, to which he has recruited hundreds of thousands of members. But it has limited his repertoire and locked him into a toxic internal spiral of constant war. Melenchon has been free to bash NATO, the World Bank, and the rich.

[Corbyn] was elected to address a crisis in social democracy from the left, when all else had failed. He would not be where he was if the people now attacking him hadn't lost all credibility.

Corbyn has been obliged to look over his shoulder. He can't withdraw from NATO and the World Bank, no major tax hikes on the rich will be announced, and energy nationalisation has been dropped. Yet he is still too left-wing for his critics, who were in more or less open revolt from day one.

The second part of the answer is Brexit. Melenchon may need less than 25 percent of the vote in the first round to have a serious chance of winning. This is because of the breakdown of the traditional centre parties - both his former party, the Socialists, and the right-wing party Les Republicains, each of which he has overtaken.

In Britain, however, Brexit has electorally consolidated the right-wing vote, with former UKIP voters deserting the party for a Conservative Party. Meanwhile, it has exacerbated the fragmentation of the left vote. In the aftermath, moreover, the Labour establishment moved to overthrow Corbyn. They hoped, through a string of resignations and timed media statements, to create an intolerable climate for him. However, they misunderstood him: he hadn't won by climbing the greasy pole. As long as members and the unions backed him, he didn't have to go anywhere: and he knew it.

Finally, they tried to oust him with another election, just one year after he was voted in. None of this worked, but it was incredibly self-destructive. At a crucial moment for the country, Labour was embroiled in factional warfare. The party plummeted in the polls. And this snap election gives Corbyn's rivals another chance to, they hope, finish the job.

It should be easy. The Conservatives enjoy a mountainous 20 percent poll lead. On a uniform swing, that would translate into 393 seats for the Conservatives and 166 seats for Labour. May, by exploiting this opportunity, hopes to break Labour as an instrument of opposition for the foreseeable future. Many on the Labour right hope that will break Corbyn: resignations designed to damage him have begun anew.

Even if this happens, however, it may not work. Not because, as some Conservatives ludicrously claim, his supporters think defeat is noble. It is because Corbyn's Labour critics don't understand why he is there. He was elected to address a crisis in social democracy from the left, when all else had failed. He would not be where he was if the people now attacking him hadn't lost all credibility. Their plotting merely makes them look like they have no answers and dislike democracy. Members will apportion much of the blame for defeat to them.

The only way the old guard could guarantee victory against Corbyn would be to engineer a more competent coup. They would have to ensure that the majority of members and trade union affiliates never had the chance of voting for Corbyn. But then they face a new dilemma. If they revert to the old pattern, where do they think that will lead? If they drive out the only new members they have recruited in years, where will renewal come from?

Richard Seymour is an author and broadcaster based in London. He has written for The Guardian, the London Review of Books and many other publications.

The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.