The ‘progressive alliance’ is one of the enduring myths of British politics. The idea that all the left-wing parties cooperating would lock the Tories out forever is so attractive a fantasy that reality can’t keep it down.

And the reality is rather brutal, as this piece in the Guardian makes clear. Even setting aside that parties of the right (Conservatives, UKIP, the Unionist parties) took more than 50 per cent of the vote in 2015, a progressive pact needed heroic levels of coordination to work even then.

Post-Brexit the maths has only got worse, and even near-perfect coordination between Labour, Liberal Democrat, and Gren voters wouldn’t prevent Theresa May getting a handy majority on current polling. But some constituencies will still try it, despite it playing straight into the hands of the Tories’ “coalition of chaos” narrative.

But it’s not just the left that falls into these traps. The Sun reports that ‘senior Tories’ are in talks with UKIP about local deals to try to protect Brexiteer MPs from the above-mentioned progressive pact.

The problem with all such arrangements is that they assume that voters can simply be herded around and reorganised at will, or that people who vote for one party of the left or right will definitely favour the rest of that ‘side’ before switching to a party on the other side.

However, this is seldom the case. Here’s another Guardian piece, this time drawing on work from the man behind Electoral Calculus, which reveals that despite the clear narrative logic of a Remain-driven Lib Dem revival there’s scant evidence of it in the data.

In fact, whilst the Lib Dems are definitely the biggest beneficiaries the Tories are actually gaining Remain voters. Such findings contradict some fundamental assumptions about voter trends in this election – yet any pact will be assembled on the basis of those assumptions.

But small gains amongst Remainers is nothing compared to the Conservatives’ inroads into UKIP’s 2015 vote, where the Party is apparently “sucking in votes like a right wing Dyson on steroids” – and picking up a chunk of 2015 Labour voters too. And if the evidence suggests that the auguries for a progressive pact are bleak it should give Brexiteers pause too.

There is certainly a big chunk of the UKIP vote which is now in the Tory column, and this could be critical in a number of seats – as we highlighted in our Battleground Seats profile of the South West. Given that, is it really to the Tories’ advantage to have the UKIP candidate stand down?

Some of the residual UKIP vote may then vote Conservative, but given how many people have made the jump we shouldn’t rule out the possibility that there are strong reasons that the remainder have not. Maybe they’re just looking for a protest vote, or perhaps they’re ex-Labour and just can’t bring themselves to vote Tory.

Now, the odds of this vote putting the Lib Dems or Labour over the line on its seems remote. It may just stay at home, as so many Leave voters had for decades before the referendum. But being so associated with UKIP may weaken the Conservatives’ hold on liberal, Remain-leaning voters (amongst whom, according to Baxter, we are making small advances even now), and push them in a direction where they could do actual damage.

Pacts and deals are interesting election news, and we’ll likely see more of them. But the dividends they offer are small, the odds of delivering them low, and they may add up to less than the sum of their parts.