S.H.
the less of a deal you make this situation, the quicker it will end. Add some repercussions to it, then it'll end even quicker.
Once I know that a child is fully potty trained, then they are responsible for all cleanup. This is not cruel, it simply teaches responsiblity. And when I say cleanup, I mean mopping - scrubbing the toilet - & all. This is done with my assistance. If it happens more than once in a day, then privileges are removed.