Another day, another shock poll: this time, one for Opinium which puts the Brexit Party in first place, with 26 per cent of the vote, Labour on second place with 22 per cent of the vote, the Conservatives in third place on 17 per cent, the Liberal Democrats just behind in fourth place with 16 per cent and the Greens on 11 per cent.

It comes after a sensational YouGov poll which put the Liberal Democrats in first place, on 24 per cent, the Brexit Party on 22 per cent, and the Conservatives and Labour on 19 per cent apiece, with the Greens on eight per cent.

And there’s one showing Labour ahead now, too: a Deltapoll survey with Labour first on 26 per cent, the Brexit Party second on 24 per cent, the Conservatives on 20 per cent, and the Liberal Democrats on 16 per cent. (No figures on the Greens that I can see but logically they must be getting a decent-sized chunk.)

What should we make of it? The same caveats I put on that astonishing YouGov poll apply here, as well, but there are also some other things worth noting now that we have a few more polls to look at.

It’s worth remembering that Opinium overestimated the performance of the Brexit party, and underestimated that of the Liberal Democrats in the European elections – they had the Brexit Party at 38 per cent, they got 31 per cent, they had the Liberal Democrats at 15 per cent, while that party actually got 20 per cent – but I would strongly, strongly counsel against drawing the sweeping conclusion that this means that YouGov (who got the European elections near to bob on) is right to show the Liberal Democrats in first place while Opinium are once again overestimating the performance of the Brexit party.

It is not really accurate to talk about the success of the Brexit Party as if it were a wholly new party: it is reaping the fruits of Nigel Farage’s national profile, the expertise of the team behind him acquired over long years in Ukip, and their established understanding of how to manipulate the press, particularly the broadcasters. Speaking of them as a new party is a bit like looking at this year’s box office figures and saying that Avengers Endgame came out of nowhere. That said, one important way that the Brexit Party is like a new party is that they don’t have campaign infrastructure in the way the established parties do.

That matters, because that infrastructure is the difference between people telling a pollster they like the Brexit Party and those same people actually getting up and going to the polling station to vote for the Brexit Party. That effect may well have been exaggerated in the European elections, as the Conservatives didn’t campaign anywhere, Labour MPs in heavily pro-Leave territory generally avoided doing so as well, and the parties which campaigned heavily, the Liberal Democrats and the Greens, did so in areas where supporters of the Brexit Party were thin on the ground.

In the 2014 European elections, Ukip benefited from their voters being brought to the polls inadvertently by strong Conservative and Labour campaigning machines on the same day. That dynamic was not in play for the Brexit Party five years later. It may be that at a general election, Opinium’s way of measuring the Brexit Party proves more accurate than YouGov’s.

The most important thing is not what separates these polls, but what unites them. One of those unifying factors is that in all of them, the gap between the first-placed party and the fourth-placed is nine points or less. That’s a situation in which our antediluvian electoral system makes it impossible to predict what the implications would be under first past the post. It could mean a yet more fractured parliament: it could mean one party forming a majority government with 25 per cent of the vote, and another being wiped out with 19 per cent of the vote.

But the most important impact is psychological: first past the post entrenches the bigger parties and punishes new entrants for two reasons. The first is that it means that political parties have to build coalitions that have geographic reach rather than simply aiming for majority support, which makes life harder for parties whose support is concentrated in a handful of areas. But the second is that because everyone knows that first past the post entrenches the big parties, it makes it harder for people to countenance voting for a small party they prefer. That’s why every Liberal Democrat leaflet since the beginning of time has featured a dodgy bar chart talking up the value of a Liberal Democrat vote in any given area and why the Greens know full well that every councillor won makes it easier for them to gain more seats at a Westminster level.

And the most important thing about all these polls have in common is that they are a drip-drip message to anyone flirting with a party other than the Conservatives and Labour that the old dynamic – where the only surefire way to prevent rule by one is to vote for the other – might not apply anymore.