I've always thought of them as a good solid source of potassium.
I just double-checked on fitday, and according to them, anyhow, a single medium banana has about 467mg of potassium, while a medium baked potato (with peel) has just over 500mg. Sounds like a decent amount to me!
Or maybe you mean "minimal" as in "not enough to immediately stop cramping"? I could buy that, if that's what you mean.