TBF - we may not have a President but all too often, especially recently, it's been the Leaders who are the ones who are deemed to be the reason a party got elected / or not elected.
There was the Johnson / Corbyn factor in the recent election.
Milliband and Cameron - although not as much as with Johnson and Corbyn.
I know we don't elect a Prime Minister but I wonder if Sunak feels if he has the mandate to be there.