In the three-and-a-half years since Jeremy Corbyn became Labour leader, barely a single week has passed in which a new example of antisemitism in the party has not come to light.

It is now so normal to read another exposé of Jew-hate from a Labour member — many in this newspaper — that the words “Labour” and “antisemitism” trip off the tongue together as if they were one.

The frequency of these examples means that they have lost the power to shock. That is a devastating comment on the poison that Mr Corbyn and his allies have injected into British politics.

Which is why it is important to step back and consider the meaning of the Equality and Human Rights Commission’s inquiry into the Labour Party.

This is not just a truly appalling moment for Labour; it should be a shocking moment for Britain itself. The EHRC will now do its work. But no one needs to wait for that work to be completed to see the scale of Labour’s institutional racism.

The party is led by an antisemite who is surrounded by antisemitic advisers — chosen because they share the leader’s antisemitic world-view.

There is a real possibility that Labour will win the next election. With that, a racist will enter Downing Street. The news of the EHRC’s inquiry has led to renewed focus on Mr Corbyn and his coterie.

But without the broad mass of the party behind him, he and his supporters would be powerless. There are many decent members of the Labour Party.

There are Labour MPs who express their solidarity with the Jewish community and speak of their anger at the party leadership. But such expressions are meaningless.

Every MP who campaigns for a Labour government is in effect campaigning to make an antisemite prime minister. Every Labour member who supports the party is likewise seeking to elect a racist PM. This may be unpalatable — but it is unarguable.