Prime Minister Shinzo Abe's cherished goal of revising Japan's pacifist Constitution has become more difficult to achieve after a plunge in his popularity and the erosion of public trust, a ruling party lawmaker said on Wednesday.

Support for Abe has plummeted to its lowest since he surged back to power in 2012 with a conservative agenda of reviving traditional values and loosening constraints on the military that centers on revising the U.S.-drafted postwar Constitution.

In May, Abe made a surprise proposal to revise the war-renouncing Article 9 by 2020 to clarify the ambiguous status of the Self-Defense Forces by 2020.