Who are those political attack ads supposed to target?

Aren’t attack ads really just to sway the undecided voters? Those who are staunch supporters of their party will not vote the other party even when their candidate is a nit twit, doofus or worse. They will not vote for who is best just who is in their party that is running. So who are these attack ads I have to suffer through everyday for? Undecided voters?

I add up which is the least slimy of 2 sleaze balls and that is who I vote for; because there is rarely any of them worth a pile of warm dog………..well you get the point.