backbencher; minor politician
Refers to a rank-and-file legislator without significant influence, often used in the context of the Japanese Diet. The term derives from the plain helmets (陣笠) worn by common foot soldiers, implying a lack of distinction.
He is still a backbencher, but he hopes to become a minister in the future.
The bill was rejected due to opposition from backbench members.
平議員 is a more neutral term for an ordinary member of parliament, while 陣笠議員 carries a slightly derogatory nuance of being powerless and undistinguished.
Compound of 陣笠 (じんがさ, 'soldier's plain helmet') and 議員 (ぎいん, 'legislator'). The term likens a low-ranking, undistinguished politician to a common foot soldier wearing a simple helmet.