Lady of the United States, Muriel had a busy schedule of travel and involvement in various causes. A catalogue of her papers at the Minnesota Historical Society gives a clear sense of the breadth of activities. She served as a member of the President's Committee for People with Intellectual Disabilities from 1966 to 1969, convened many meetings of women associated with the Democratic Party, and travelled extensively. During her husband's subsequent run for president in 1968, Muriel made a number of public appearances, garnering praise from President Johnson. After Hubert lost the 1968 election to former Vice President Richard M. Nixon, he made a decision which would ultimately lead to Muriel's entry into politics: He chose to run for a US Senate seat from Minnesota in the 1970 elections. Hubert won the election and returned to the Senate in January 1971. Hubert Humphrey died of bladder cancer on January 13, 1978. He was 66. Muriel was nominated by the Democratic-Farmer-Labor Party and subsequently appointed to the Senate vacancy by Minnesota Governor Rudy Perpich, serving from January 25, 1978, to November 7, 1978, in the 95th Congress. She was the first spouse of a former vice president to serve in Congress as well as the first woman to represent Minnesota in the U.S. Senate, preceding the Democrats Amy Klobuchar and Tina Smith. Muriel had years of experience as a public speaker, and was an active senator. According to Karina Karr, Humphrey was ostracised by the all-male Senate, but served on the Foreign Relations Committee and voted reliably to support the foreign policy of the Jimmy Carter administration. According to an official Congressional biographical summary, "Muriel Humphrey pursued her own interests during her brief tenure, supporting an extension of the Equal Rights Amendment (ERA) ratification deadline and advocating several programs to benefit persons with mental disabilities." Among the issues which she championed was public visibility for Down Syndrome, a topic she had become passionate about due to her granddaughter Victoria Solmonson's condition. During her husband's presidential campaign in 1967 and 1968, she visited facilities for people with Down Syndrome in Long Island and was featured by the New York Times. In 1970, she gave a speech on this topic which was reprinted in a prestigious medical journal. As a senator, she sponsored the Mental Health Advocacy Act of 1978. After consulting with President Jimmy Carter, Muriel chose not to stand as a