“No man has a good enough memory to make a successful liar.”

"Successful" would here have to be defined. MSM, current politicians, seminary evangelists (government school teachers) as well as most other patrons of the occupying statist theocracy infesting this land have certain lying facades, dogmas and history they maintain regularly. As Joseph Goebbels said: "Repeat a lie often enough and it becomes the truth" (varying orations don't seem to matter much). Also-and/or, the ole adage: "the adversary will tell you a thousand truths to make you believe one lie", comes to mind.

Fidelity to Reality and attendant discernment make the defining difference.

In this day of infidelity to Reality and of dramatically diminished and further diminishing discernment, a shameless prevaricator need only be charismatically persuasive, in his or her ability to cultivate frailties of fallen human character, to experience "success".

Acuity of memory is hardly a factor, much less a necessity.

Not anymore... the go-to defense for any lying politician is "I don't recall."  The world is full of successful liars!  The bad memory resides with those that believe them.