The two greatest dictators in history, Hitler and Napoleon, rose to power in countries who cut ties (or heads) to their royal houses and formed Republics.
Are there any similar cases of royalty reasserting absolute power after democratic institutions have handled governing powers for a time?
My basic thought is that people in crisis will be willing to hand over absolute power to someone. This is human nature. In a republic, a charismatic leader can harness this fact to his own ends, to the detriment of the people.
In a constitutional monarchy, the charismatic leader has an obstacle to capturing the nation's vision of itself, because there is already a personal symbol at the top. As long as the monarch is there, the proto-dictator cannot overwhelm the nation's self-identity.
In this model, the only way for a constitutional monarchy can decend into dictatorship is if a royal is also a charismatic leader. Which has maybe happened two or three times in the past 1000 years in England. And then that would have to be coincident with a crisis.
I agree that this model is simplistic, many of the same things that could lead to an elected charismatic leader in a republic could happen in a constitutional democracy, but I suggest that a monarch is one more obstacle for that to happen.
Edit: In response to Can 'o worms:
1) The fact that there are a greater number of Quebecers who oppose the monarchy does not mean that it's a problem. Separatists are pissed off because:
We instituted martial law in their Province after two government officials were kidnapped by terrorists.
We repatriated the constitution and enacted the charter of rights when their government opposed it.
We drafted their boys into WWI and several protesters were killed by the police (still smarts for them)
We consistently elect centralizing governments when they want more freedom to govern as they see fit.
Alberta gets pissed whenever we let them out of centralized programs, and that offends them.
Several attempts to reform the constitution since the repatriation have been thwarted by Alberta and interest groups.
They fear the loss of their language and culture.
The only reason that they don't like the crown are because of the draft thing and the whole conquering thing. Both history out of most people's living memory. Small potatoes.
2)I cite my argument above, and point out that it can be dangerous. But a republic may be more dangerous. Lesser of two evils.
3)Both Sweden and Norway spend about 8.5 million dollars to support their monarchs. A drop in the bucket.
Link Canada spends no money for the day to day activities of their monarchs. We only spend money on them when they make official visits, which is rare. And we probably spend alot when foreign heads of state visit, which we would still have to do when they came. What we spend on the Governor General is what we would likely spend on an elected head of state, plus the cost of the election. Possibly more, since an election might make them more popular, and therefore more likely to recieve funds.
4)An irrelevant question until the heir is no longer an Anglican. Call me when Prince William becomes a Buddhist. (Come on, you know it's gonna happen)
5)The royal family represents the history of our nation. I'd rather have that than someone who represents nothing more than the money they could cobble together to win an election. Since the hypothetical "President" would have no real power, so the election would be no more than a popularity contest. I shudder at the thought of Celine Dion as our head of state.