In his youth he was active in the Jewish Socialist Party, the "Bund" followed by "HaShomer Hatzair" but in 1925 he joined the Revisionist Zionist Movement.

[3] In September 1939, Bader moved to East Poland, then under Soviet rule; he was arrested and sentenced to hard labor in northern Russia in 1940.

In 1941, he was released under the terms of the Soviet-Polish Agreement and left the Soviet Union; in August 1942 he joined the Free Polish Army.

[4] He was member of the Knesset for Herut and its successors, Gahal and Likud, from 1949 to 1977, a regular member of the Finance Committee, and was the economic spokesman of his movement; he is remembered for his rhetoric debates with former Minister of Finance Levi Eshkol.

He is famous for the amendment to the election law, which became valid since the elections to the Eighth Knesset, according to which the excess votes are distributed to the lists with the largest number of voters per seat – a method known in the world as the D'Hondt method, and is known in Israel as the Bader-Ofer method – named after Bader (Gahal) and co-proposer Avraham Ofer (Alignment).