Shinzo Abe faces plenty of roadblocks in his quest to revive Japan's sluggish economy. His mentor wasn't supposed to be one of them.

Former Prime Minister Junichiro Koizumi is easily the most popular Japanese politician of the last 20 years. Not since Yasuhiro Nakasone in the mid-1980s had a Japanese leader made such a splash domestically and globally. Not coincidentally, both were keen reformers — as Abe, too, claims to be.

After he left office in 2006, the now-71-year-old Koizumi seemed happy to stay in the shadows. That changed last month, when he made a very public about-face from his previous support of Japan's nuclear industry. "Nothing is as costly as nuclear power generation," Koizumi said in an Oct. 1 speech, arguing that Japan "could do well without" the dangerous reactors on its seismically active shores.