From the Document: "On January 30, 2019, Senator Elizabeth Warren and Representative Adam Smith introduced legislation (S. 272/H.R. 921) that declared, 'It is the policy of the United States to not use nuclear weapons first.' Other Members of Congress are divided on this issue. Senator Dianne Feinstein has argued that the only moral use for U.S. nuclear weapons is as a deterrent to their use. Senator Deb Fischer, on the other hand, has said that the proposal 'betrays a naïve and disturbed world view.'"
CRS Report for Congress, IN10553
Congressional Research Service: https://crsreports.congress.gov/