Again and again Trump ran over the time limits while constantly interrupting Hillary Clinton.
Sooner or later, the moderators just gave up, if they challenged him at all.
To be fair, Clinton also ran long and interrupted, but nowhere near the level of Trump.
I suspect the conditions of the debates were negotiated beforehand, so I gather the moderators were helpless to enforce any limits.
And I'll guess there's no chance the below suggestions could be incorporated into the final debate on Wednesday, Oct. 19 (9 p.m.).
But here's some ideas on how to rein in the candidates:
1) Have an unobtrusive light blink as the limit nears. (I believe this has been used in the past.)
2) A candidate who goes beyond (or say, over more than a few seconds) the limit has his or her microphone shut down.
3) And why not this: Punish and reward candidates, by subtracting from their future time when they interrupt their challenger(s) and adding to the time of candidates respecting the other's time.
Now all we need is for a candidate in the next election to publicly make these conditions the requirements for him or her to take part in any debates.