Raymond B. Harding, the former vice chairman of the state’s Liberal Party, pleaded guilty Tuesday to a felony related to securities violations under the Martin Act, the latest development in Attorney General Andrew M. Cuomo’s investigation of the state pension fund. Mr. Harding had been accused of accepting more than $800,000 that prosecutors say was a reward for doing political favors for the former state comptroller Alan G. Hevesi. Saul Meyer of Aldus Equity, a Dallas-based firm, also pleaded guilty on Friday to a Martin Act felony in the case. Mr. Meyer was a top consultant to pension funds around...