The merits and drawbacks of democratic government come from the responsibility of the people themselves to choose their leaders, and thereby, sometimes directly, sometimes indirectly, choose the path the nation will follow.
This election cycle has been particularly interesting because of the controversial nature of the candidates. Donald Trump gives voice to what has been a vocal but outnumbered wing of the Republican party. His views appeal strongly to some and horrify others. In a democracy it is possible for such a candidate to draw enough support to make a serious run at winning office because voters can be unpredictable--sometimes they are moved by momentary political pressures that might not be successful in the long run. If we lived in a less democratic society, a candidate like Trump might have a harder time making a strong run, even with the same sort of support that he has right now.
The same could be said of Bernie Sanders' campaign. He gave front runner Hilary Clinton a much tougher battle than most expected. Again, this may have been due to temporary political pressures. The recent recession left many voters and their families worse off than they had been previously, which widened the interest in Sanders' liberal ideas of helping middle and lower class families economically. As a result of his strong run, Clinton had to move to the left a bit to weaken his base.
Since electoral decisions rest with the voters, politicians must find ways to appeal to them. Voters are fickle, and not always very well educated, which means that politicians don't necessarily have to present sound ideas, they just have to present ideas that sound good. Can the voting public discern the difference? How well they do so determines to what extent voters are either the strength or weakness of their democracy.