Politics seems to run in families. The question is: why? Why would electors choose the son, daughter or spouse of a successful politician over other candidates who are, on paper at least, equally or more qualified?
An economist is in no position to answer this question, but is ably equipped to theorize about it.
Theory 2: Politicians are like hockey players. No one can hope to be a successful hockey player unless he learns to skate as a child. Because hockey players teach their children critical skills during the right developmental windows, those children have a disproportionate chance of professional success. In the same way, the son or daughter of a successful politician imbibes confidence, leadership style, and an ability to rule during their childhood. This early training gives them an unbeatable advantage over rivals.
In both Theory 1 and Theory 2 parentage is a signal of a candidate's true, underlying ability. Political dynasties have merit because the offspring of politicians will, on average, be more able than other candidates. Yet there are other possible theories.
Theory 3: Political networks are bequeathable. Children of politicians grow up surrounded by influential and well-connected people. As adults, they can call upon those networks for support.
Theory 4: Voters look for sunspots. Electors have little information about a candidate's abilities and policies, but they have to coordinate on the choice of a leader. They use parentage in the way that markets use sunspots - as a way of picking one leader from a crowd of equally qualified potential leaders.
I find the media and public obsession with Justin Trudeau hard to understand, but my guess is that it is better explained by Theories 3 and 4 than Theories 1 and 2.
In my view, Mr Trudeau has little chance of achieving the kinds of electoral victories that his father enjoyed. Here is one theory as to why.
A politician's observed characteristics, for example, his or her employment history, speaking ability, support within the party and policy platform, are a function of both "training" and underlying intrinsic ability. The scion of a distinguished political family is endowed with a higher level of training than the average politician, hence requires less underlying intrinsic ability to acquire the same observed characteristics. In the long run, however, it's intrinsic ability - intelligence, people skills, political intuition - that matters. Therefore, unless the politician coming from the privileged background is clearly much superior to the other candidates, I would opt for the self-made politician every time.
On the other hand, the candidates I support almost never win elections.