Do you think that what H L Mencken wrote 70 years ago, about politics, still hold true today, or has politics changed?

Mencken had it right and there has been no change.

Mencken said a lot of things. Do you have a particular quote in mind or just his general tenor?

I think it does, a couple of them are:

"The whole aim of practical politics is to keep the populace alarmed — and hence clamorous to be led to safety — by menacing it with an endless series of hobgoblins, all of them imaginary."

And, "The urge to save humanity is almost always only a false face for the urge to rule it."