Joking aside, elections very often tend to be on single topics.
Cameron - Economy
Cameron II - Miliband can't eat a sandwich
May - Brexit Deal and not Corbyn
Boris - Above
Starmer - Not the Torys
As much as we ridicule them, I feel fairly sure the next election will be 99% on immigration and the parties trying to out Farage, Farage. Genuinely think he'll win.