As Tokyo presses North Korea for information on the fate of Japanese citizens abducted decades ago, speculation is simmering that Prime Minister Shinzo Abe could use a possible breakthrough on the emotive issue to call a snap election.

History shows that securing the release of Japanese kidnapped by the North decades ago can deliver a hefty, if short-lived, boost to popularity.

North Korea agreed in May to reopen an investigation into the fate of missing Japanese, including those snatched by its agents to train spies in the 1970s and 1980s, in return for the easing some economic sanctions on the reclusive state.