He finished first in a four-way primary race and defeated three-term incumbent George Colella 11,356 votes to 9,394 in the general election.

In 1974, Reinstein ran in the special election to succeed the deceased Torbert Macdonald as the U.S. representative from Massachusetts's 7th district.

He finished sixth in a twelve-candidate Democratic primary that was won by state representative Ed Markey.

In 1976 Reinstein was indicted for bribery and perjury after a yearlong investigation into alleged kickbacks during the construction of Revere High School.

The judge found this ad to be a "direct breach of the understanding and commitment which has led to ... an unsequestered jury.

[12] During his tenure in the state house, Reinstein was a supporter of the death penalty and opposed abortions with exceptions of rape and incest.