Why are so many lawyers politicians?

Johan Richter, a loyal MR reader, writes to me:

As the primary elections are coming up is is interesting to note that so many of the contenders are lawyers, something that is also true of the members of Congress, where I believe half are lawyers. Why are so many US politicians lawyers? It seems odd considering that A) Legal training seems unnecessary for performing the main job of a politician, regardless of whether one takes that to be courting public opinion or governing the country. And there is hardly any deficit of lawyers in Washington to ask for advice if legal knowledge turns out to be needed. B) Being a lawyer isn’t very prestigious as far as I know. Being a military, doctor, police officer, businessman or perhaps even a academic would surely be regarded by many voters as more respectable professions than being a lawyer. C) Other countries don’t have nearly the same over-representation of lawyers in their parliaments as the US does.

I thought Google would yield a paper on this question but I can’t find it.  My guess is that lawyers are good at fundraising and good at developing personal contacts.  This helps explain why fewer politicians are lawyers in many other countries; money is more important in American politics.  A lawyer also has greater chance to exhibit the qualities that would signal success in politics, such as the ability to persuade and the ability to speak well on one’s feet.  Not to mention that many lawyers have ambition.

Natasha, who is a lawyer, adds that law generates an outflux of people to many other fields, not just politics.  There is also a path-dependence effect, by which a previous presence of politicians in law breeds the same for the future.  What else do you all know about this?

Addendum: I’ve posted a version of this query over at Volokh.com as well; I expect they will have something to say about the question.

Second addendum: Over at VC, Shawn says:

You will also find that Real Estate and Insurance agents are
disproportionately represented in politics, at least at the more local
levels.

These professions (along with practicing law) provide the career
flexibility for would be politicians to put their jobs on hold or scale
them down a few degrees while pursuing elected office or serving is
such an office.

This flexibility also is what attracts people who wish to be career
politicians, so that they have a job to fall back on between election
seasons that won’t trap them into long term obligations, keeping them
from the next election cycle or serving if elected.

These careers also give would be politicians a good place to get recognition and network within their communities.

Third addendum: Bob Tollison writes to me: "McCormick and I devote a chapter 5 to why lawyers
dominate legislatures in our book– Politicians, Legislation and  the
Economy, Martinus Nihoff, 1981. Lawyers are better at combining being in the
legisture with making outside income. Hence, lawyers dominate low legislative
pay states because seats have a higher present value. Women dominate high pay
states."