Ishibashi was conscripted in 1944 and later reached the rank of apprentice officer by the end of World War II.

Only a few months preceding the 1983 general elections, Ishibashi assumed the role of chairman for the Japan Socialist Party (JSP).

Unfortunately for Ishibashi, this program did not convince voters that meaningful reform would come from the JSP (as opposed to mavericks within the LDP such as Prime Minister Yasuhiro Nakasone), and as a result the JSP lost 27 seats in the 1986 general elections, and also saw its popular vote fall by 2.26% compared to the previous 1983 election.

In later years, he acted as an advisor for JSP chairwoman Takako Doi in strengthening cooperation with centrist parties.

Ishibashi's reputation as an inter-party compromiser was seen in the fact that he refused to go along with chairwoman Doi's request that Ishibashi help campaign for an ambitious 180 candidates being fielded by the JSP for the 1990 general election, as this would involve hurting the electoral prospects of centrist allies.