“talk or write persistently and tediously on (a particular topic).
“I don’t want to harp on about the past”
Perhaps you should make use of the dictionary.”
Perhaps you should read your own posted definition. It says, to repeat, to “talk or write persistently and tediously on a particular topic.”
In a given speech or talk, Trump mentions it, sometimes with with few sentences. In a ninty minute speach, a few minutes.
That is not a persistently and certainly not tedious. The Russian hoax by the MSM and democrat politicians is a good example of persistent and tedious.
And yes, it is good to harp on certain things. It is normally called warnings, a technique used by all societies throughout all history.
Wordsmithing is not your strong suit especially when debating an issue