Triangulation
Chasing “undecided” voters is a lot like chasing unicorns. But even if they do truly exist, they are such a statiscally vanishingly tiny percentage of the electorate that it’s berserk to pursue them.
At least in recent times, the way elections are won is by mobilizing your base. And if you don’t address issues of critical importance to significant segments of your base, it’s unlikely you’re going to win.