After taking Japan's helm for the second time in December 2012, Prime Minister Shinzo Abe has had three good years, leading his Liberal Democratic Party to victory in two consecutive national elections, getting highly unpopular laws enacted without dooming his Cabinet, and winning three more years as chief of the conservative party until September 2018.

As Abe enters the second half of his term, he will face a major challenge in 2016: the Upper House election.

For Abe, the summer contest will be a fight for his and his revered grandfather Nobusuke Kishi's long-cherished goal of revising the war-renouncing postwar Constitution, observers said.