Why did President Carter not fight for SALT II?

President Carter did not aggressively pursue the ratification of the SALT II treaty due to a combination of factors, including escalating tensions with the Soviet Union following their invasion of Afghanistan in late 1979. This event shifted U.S. public and political sentiment against the treaty, as many viewed the Soviets as untrustworthy. Additionally, the growing focus on military preparedness and defense during this period made it politically difficult for Carter to advocate for arms control measures that were perceived as limiting U.S. capabilities. Ultimately, these dynamics led to the treaty's failure to be ratified.