An outraged Sen. Alan Cranston, D-Calif., charged politics have played a role in the Senate Ethics Committee investigation of five senators and their relationship with the head of a troubled savings and loan.

In a letter to committee members Tuesday, Cranston asked whether he is the "logical scapegoat" in the S&L scandal and if "politics is playing an improper role" in the ethics panel's deliberations.Cranston, under treatment for prostate cancer, has already announced he will not seek re-election in 1992 and did not run for his leadership post in the Senate.

Cranston and Sens. Dennis DeConcini, D-Ariz., John McCain, R-Ariz., Donald Riegle, D-Mich., and John Glenn, D-Ohio, are under investigation on charges they tried to pressure the Federal Home Loan Bank Board on behalf of Charles Keating, who contributed $1.3 million to their campaigns and causes.

The ethics committee is in the final stages of its work and is expected to make its recommendations before the end of the week.