Well, I suppose all govt. is unstable, then. Which dynasty has been in power forever?

Stability is a matter of degree, as you're well aware. Few dynasties lose power after four years of rule.

What good is that going to do a peasant like me? It's not like they are going to knock off the cost of electioneering from my taxes.

Even a massive amount of spending on election campaigns is less likely to succeed (and thus less stable) than a (relatively) small amount of spending an safeguarding from assassination.

Also, election campaigns have negative effects on, among other things, the rationality of the populace; and they encourage polarization in the long term - in contrast, bodyguards discourage trying to off your rich uncle for the inheritance.