Potatoes are a lot better food than they get credit for, but in a world where the majority of people are overweight we need to look at micronutrient density relative to calories before food weight.

A modest bunch of spinach packs almost 2g of potassium for under 100 calories. That sounds like a lot of spinach until you cook it--it shrinks a ton. You'd need like 500 calories worth of potatoes (or 700+ calories from a nice bunch of those overrated bananas) to match.

In general, all those leafy green and cruciferous vegetables that people hate are very favorable in micronutrient density to macronutrient content, potassium included.

Meat, beans, and potatoes are all "decent" potassium sources, but particularly in the context of sodium/potassium balance (which seems to have at least as much bearing as raw intakes do) and how hard it is to keep sodium intake down, it's hard to get enough potassium without at least a little bit of veggie love.