Who would benefit from a significant Labour breakaway? That’s the question being asked in the wake of my cover story in this week’s New Statesman about the growing number of Labour MPs who have decided, come what may, that they must leave the Labour Party.

Frankly, with the shape, scale, leadership and platform of the breakaway still unknown, it’s all a bit of a mug’s game. Anthony King and Ivor Crewe’s definitive study of the Social Democratic Party, which broke away from the Labour Party in 1981, showed that that party did not, despite what many in Labour believe, decisively alter the 1983 election result one way or the other. But a lot has changed since 1983, so it may be that a new party hurts Labour more than the Conservatives. That is certainly the fear of some within the Labour Party, and for some of those considering a split, it is part of the attraction.

Ultimately, it’s anyone’s guess, but I am unconvinced. We know that the known unknown of Labour’s 2017 coalition is the third of voters who voted Labour in 2017 but, when asked who they preferred as prime minister, replied with either “Theresa May” or “don’t know”. Were I the Labour Party, this section of the electorate would be keeping me up at night.

The big decision point for this group will be: do its objections to Jeremy Corbyn outweigh their desire to kick the Conservative Party out of office? Thanks to our iniquitous first-past-the-post electoral system, everyone knows that the risk you are taking in not voting for one of the big two political parties is in letting the other one in. What matters is if the new party is attractive enough to make the risk worth taking. But frankly, Labour voters with doubts about Jeremy Corbyn are already pretty well served with alternative political parties: if they are looking for something still on the centre-left but to Labour’s right, there are the Liberal Democrats. If they want something more radical, or without the foreign policy baggage, there are the Greens.

My feeling is this group is going to stick or twist at the next election regardless of what is offered for them. What really matters is if Labour can woo them enough. Increasing the size of the menu on offer to them is not going to be a gamechanger.

There is a gap in the left marketplace for what we might call welfarist authoritarianism: high levels of public spending, but with a tougher stance on immigration and defence than that favoured by Corbyn. But that isn’t a political brew that any of Labour’s would-be splitters are likely to serve. Instead, it looks a lot more likely that they will be another entrant in that lefty cosmopolitan space that is already well served by competitors on the left.

But what there isn’t really is a party that is making serious overtures to Conservative voters who liked David Cameron but are unsure about Theresa May, which accounted for around 15 per cent of their 2017 vote is not keen on Theresa May. That 15 per cent is overwhelmingly pro-Remain but is not, as of yet, voting Labour. Given the awfulness of the 2017 campaign and the state of Brexit, it’s not unreasonable to believe this group will never vote Labour in its current form.

Don’t forget, either, that it is the Conservative Party that looks to be headed straight for a calamitous and unplanned exit from the European Union. When new parties succeed, it tends to because of a wider change in the political ecosystem: an enfranchisement of new voters, a changed electoral system, or some disaster that befalls the country. And again, some of the voters who may be aggrieved over the consequences of an unplanned exit will want an option other than Labour.

All of which is why I think a new party poses a greater risk to the Conservatives, rather than Labour.