“nearly all men can stand adversity, but if you want to test a man's character, give him power.” ― abraham lincoln. what does this mean?

In order to know how someone is (or their character) you must put them in power. if you give someone power it is easier to see what their motive is.

Yes, this question is hard to explain, so let me try.  Sometimes men think power is their only advantage.  You can see examples, like when the 37th president Nixon thought since he was the president, the had the right to keep his conversations secret.  But this is not true, no one is above the power of law.  Any who, men change their personality when they are given power.  They think differently, and act differently.  Sometimes this is yet a bad thing, other time a good thing.  But this quote is trying to say, power brings out a mans inner self.