Yesterday was a watershed moment for the Reform Party. They had what is known as a "crossover" moment - overtaking the Tories in a mainstream poll.
Polling from YouGov, published yesterday, saw Reform's support increase by two points to 19 per cent. The Tories remained unchanged on 18 per cent.
Worryingly for Sunak, the polling was conducted after the Conservative Party published its manifesto on Tuesday.
The polling shows that the dial has moved in Reform UK's favour. But not only that, in itself, polling like this can push the dial even further. If Reform is lucky, it could cause a snowball effect.
Responding to the poll this morning, Richard Tice said it shows his party is finally being seen as a "serious credible alternative option".
"The momentum is with us", he said. And he's exactly right.
Many people have long seen Reform as a protest vote. A fringe option to demonstrate exasperation with the Tories' offering.
What may have put many voters off from backing Reform, is the idea that the party won't win any seats. The view that they're a fledgling party without a real support base.
Symbolically, Reform UK overtaking the Tories is huge.
While the party may still win far fewer seats than the Tories - as a result of having a thinly spread support base in a First Past the post voting system - polling like this will go significant distance in persuading voters that a vote for Reform UK is not a wasted vote.
We saw Farage attempt to capitalise on this very issue last night, when he told ITV's Leaders' Debate that Reform UK is the "official opposition to Labour".
He later said that a vote for the Tories is now a vote to enable a Labour government, in a flip of Conservatives’ campaign rhetoric.
The Tories should be very afraid of this. If Reform can keep itself ahead in the polls, the effect could get bigger and bigger.
Once Tory donors see that their horse in the race is backsliding, ones who sit on the right of the party are likely to jump ship to Reform. Even Tory candidates - if local polling suggests that Reform UK is more likely to take the win in their constituency, they will once again be more likely to jump ship to Reform.
And with more donors, more established candidates and higher positioning in the polls - the votes will follow.
A boost in the polls is self-reinforcing - and Sunak should be very concerned.
