Reform are doing to Sunak what UKIP did to Cameron. Attracting just enough Tory votes to cause panic and encourage concessions to the barmy right.
My guess is for every vote gained they lose at least one off the other end. Because not all Tories are swivel loons, many are moderate and pro-EU. Especially darn south.
The tail is wagging the dog, rather like Momentum did in the Labour Party. What these people (at both ends) fail to understand is that what is popular among the politically obsessed is not necessarily what is popular among the general population. Most ordinary punters care about trifling things like job security, affordability of rent/mortgages, education of their kids, the cost of food and utilities, and the NHS. I know this stuff is dead boring compared to foreigners popping across in small boats, but it's what moves the bulk of the population.