Prof. Frank MacKinnon, in his landmark study, The Crown In Canada (Glenbow Alberta Institute, 1976), notes that "heredity permits apprenticeship." Heredity, he writes, has not been kept around for the sake of privilege; rather, it has been kept around for practical purposes, an argument which in my opinion holds far more water than those dealing with "custom," "history," or "tradition."
“For a prime minister in country with a constitutional sovereign,” writes Prof. MacKinnon “the latter is a remarkable official with useful experience which no one else can command. Born and trained to the job, he is usually well acquainted with public men throughout the world, privy to what goes on behind the scenes in government, informed on the successes and mistakes of countless officials, knowledgeable on public issues and how they are handled, informed on public opinion, completely independent of politics, and without ambition for higher office because there is none.”
Heredity also ensures that the headship of state remains "completely independent of politics." While I realise that this argument has become something of a monarchist cliche, it makes a good deal of sense. Canadian republicans often seem to suggest that an ideal Canadian president could come about through a nation-wide popularity contest. The only requirements would be that they live here and conform to all of the right "Canadian" stereotypes. We would thus end up with an overtly-ambitious politician or a popular, but otherwise inexperienced celebrity as our head of state.
"Constitutional monarchy," writes Michael Valpy, "is about stability. “The king is dead, long live the king.” One sovereign dies, and the title passes to the next one in line to become the personification of the state and the person in whose name the state acts. For Canada and 15 other countries, Charles is next in line to succeed his mother. Start playing around with the succession – we like this person, we don’t like that person – and the core value of stability is undermined. Suddenly, the person becomes a political choice backed by factions. Bleh."
This last point is crucial. In almost every republic, the president is chosen through some kind of preselection process. More often than not, the winning candidate is chosen only because he or she is politically-acceptable to the government of the day (a situation that is common in countries like Germany, India, and Italy, all of which have mainly "ceremonial and symbolic" presidents). "The sovereign," writes Prof. MacKinnon, "must be non-partisan; election tends to give a head of state a partisan image and thereby fragments the public support he should have." Groups like Citizens For A Canadian Republic need to understand that the apolitical headship of state to which Canadians have become accustomed risks being politicized in their quest to establish a "purely Canadian" system.
I'm sure that those who are unhappy with the hereditary system would be just as unhappy with a system in which they had to declare a political preference for a supposedly apolitical position. No system is perfect, but our constitutional monarchy has worked rather well for almost a hundred and fifty years. Changing it on the sole basis of petty nationalism would be unnecessarily silly.