"Who is this Aso?" This was the question, verbatim, Tokyo-based strategist Nicholas Smith asked in a 2008 report on Japan's new prime minister of the moment, Taro Aso.

Like most Japanese leaders back then, the hapless Aso lasted a year. One of Shinzo Abe's main contributions to Tokyo politics is stopping that revolving door. He'd rotated through it himself once before — from 2006 to 2007. When he returned to power in 2012, Abe pledged to stick around for a while. At the time, pundits joked that Japan had changed the meaning of "Group of Seven," the number of leaders it had in six years. Abe's point was a good one: so many changes at the top dent Tokyo's stature and leave no time for a reform-minded government to change things.

Abe erred, though, by bringing one of those revolving-mandarins with him, the above-mentioned Aso, to be his finance minister.