Letting people do it totally passively, however, could be bad. We know that people lean heavily towards default behavior when possible. So if the person you mirror starts deviating substantially from what you expect of them, you will be unlikely to change your preferences in a timely manner.
Consider that under our current system of representative democracy, politicians are typically up for re-election only every ~4 years, incumbents have a strong advantage in elections, and people ideologically cling to a single party for an entire lifetime. If my idea were the status quo and you suggested a shift to our current system of representative democracy, I might point to gerrymandering or the possibility of a hung parliament as arguments against such a shift.
It'd be easy to have peoples' political preferences expire every X years and force them to re-confirm them. To simulate the effect of term limits, you could cap the number of votes a person could control or the duration for which a person could have their votes be auto-copied.
There's a whole host of other problems with such a system
Go on if you like!
people ideologically cling to a single party for an entire lifetime.
[Citation needed]
Counter-meme: "If you're not a liberal at twenty you have no heart, if you're not a conservative at forty you have no brain."
Politics as gymnastics for rationalists. No one one Less Wrong is quite sure why politics is a taboo topic or how things got to be that way. What we do think we know is that politics is a great way to bring out the irrationality in people. So why not take advantage of that and use politics as a way to measure rationality? Since politics brings out the most irrationality, it should provide the strongest signal. Since there aren't useful objective metrics of how a political discussion went, we'd have to use subjective judgements by neutral third-party raters, kind of like they do in gymnastics. (In the comment thread for this post, feel free to find fights that you have no dog in, improvise a rationality rubric, and grade participants according to your rubric... let's see how it goes.)
Be a sheep. This is probably the exact opposite of what you were taught in your high school civics class. But if my friend Jane is more intelligent, more informed, and less ideological than I am, it seems like voting however Jane is going to vote is a strict improvement over voting however I would naively. It also saves me time, and gives Jane an incentive to put even more time in to carefully considering political issues since she now controls two votes instead of one. Done on a large scale, this could provide an interesting twist on representative democracy. Imagine a directed graph where each node represents a person and an edge is directed from person A to person B if person A is auto-copying person B's votes. There's a government computer system where you can change the person you're auto-copying votes from at any time or override an auto-copied vote with your own personal guess about what's best for society. Other than that, it's direct democracy... all bills are put before all citizens to vote on. Problems this might solve: