A leader is politically legitimate when citizens accept his right to lead them. They willingly cooperate, accepting his decisions even when they disagree, because they trust his intentions will be in accord with their nation's broadly accepted laws and practices.
Congressman John Lewis will not be attending the Presidential Inauguration Ceremony on Friday because he believes the incoming President is not legitimate. Lewis cites illegitimate means the President-elect's campaign used to secure his victory — but that is not the test of legitimacy. What matters is whether or not the mass of the American public accepts that Tr*mp is entitled to lead. It is not a matter of how he achieved office, but of how willing Americans are to follow his leadership.
A significant minority of the American public never granted legitimacy to Barack Obama. They were emotionally incapable of accepting the leadership of a black intellectual, so were willing to believe he was a foreign-born socialist Muslim A recalcitrant Republican Congress acted as if that minority's misguided beliefs were true — but Obama had sufficient public support to guide the direction of the country through eight years in office despite bitter opposition.
Whether Tr*mp will enjoy that level of legitimacy remains to be seen. His significant deficit in the popular vote is working against him, as well as his bizarre affection for Vladimir Putin — but the emotional element is key. To many Americans, his innate persona inspires feelings ranging from distaste to utter contempt.
It is true that most people just make do with whatever government they get, so many authoritarian governments manage to persist by coercive repression of a small number of vocal opponents. If the opposition is sufficiently vigorous, though, even those governments fail.
