The way I see it, politics doesn't have any qualifications. Sure, a lawyer needs to have a law degree to practice, and a doctor needs a medical degree, but in those two professions, you need to be able to know basically everything about the specific task you are supposed to be performing, whereas there is no possible way that anyone could know everything about running a country, even ex-Presidents. It's much less of an exact science and much more of a set of good and bad choices.
Also, more to the point, political office is one of the very few 'professions' (if you can call it that) that requires absolutely no formal qualifications at all, so the comparison is absurd.
Since the thread has gone for many posts now debating one posting of a "simple truth", I'll put my thoughts in, too.
Political office has one very important qualification - getting elected.
Getting elected is not easy and requires definite skills. A successful candidate for office has to be able to convince a majority of the electorate to give them their vote. Just as lawyers may succeed by different skills, such as excelling at trials or in crafting strong contracts, politicians can succeed with different skills, too. Some may succeed by being well known and trusted from their resume. Some can craft and deliver a message that matches the political views of the voters. Some rely on their ability to connect with voters on a personal level. Most succeed with a blend of skills like these, but tend to lean on just one or two primary skills to make their case.