His popularity as Indiana Governor, and the state's status as a critical swing state, helped him secure the Democratic vice presidential nomination on a ticket with Wilson in 1912 and win the subsequent general election. An ideological rift developed between the two men during their first term, leading Wilson to limit Marshall's influence in the administration, and his brand of humor caused Wilson to move Marshall's office away from the White House. During Marshall's second term he delivered morale-boosting speeches across the nation during World War I and became the first U.S. Vice President to hold cabinet meetings, which he did while Wilson was in Europe. As he was President of the United States Senate, a small number of anti-war Senators kept it deadlocked by refusing to end debate. To enable critical wartime legislation to be passed, Marshall had the body adopt its first procedural rule allowing filibusters to be ended by a two-thirds majority vote—a variation of this rule remains in effect.
Marshall's vice presidency is most remembered for a leadership crisis following a stroke that incapacitated Wilson in October 1919. Because of their personal dislike for him, Wilson's advisers and wife Edith sought to keep Marshall uninformed about the president's condition to prevent him from assuming presidential powers and duties. Many people, including cabinet officials and Congressional leaders, urged Marshall to become acting president, but he refused to forcibly assume the presidency for fear of setting a precedent. Without strong leadership in the executive branch, the administration's opponents defeated the ratification of the League of Nations treaty and effectively returned the United States to an isolationist foreign policy. Marshall is also the only known Vice President of the United States to have been exclusively targeted in an assassination attempt while in office. Marshall was the first Vice President since Daniel D. Tompkins, nearly a century earlier, to serve two full terms.
Marshall was known for his wit and sense of humor; one of his most enduring jokes, which provoked widespread laughter from his colleagues, came during a Senate debate in which, in response to Senator Joseph Bristow's catalog of the nation's needs, Marshall quipped the often-repeated phrase, "What this country needs is a really good five-cent cigar." After his terms as vice president, he opened an Indianapolis law practice, where he authored several legal books and his memoir, Recollections. He continued to travel and speak publicly. Marshall died while on a trip after suffering a heart attack in 1925.
Thomas Marshall's paternal grandfather, Riley Marshall, immigrated to Indiana in 1817 and settled on a farm in present-day Whitley County. He became wealthy when a moderate deposit of oil and natural gas was discovered on his farm; when he sold the property in 1827 it earned $25,000, $523,750 in 2015 chained dollars. The money allowed him to purchase a modest estate and spend the rest of his life as an active member of the Indiana Democratic Party, serving as an Indiana State Senator, party chairman, and financial contributor. He was also able to send his only child, Daniel, to medical school.
Marshall's mother, Martha Patterson, was orphaned at age thirteen while living in Ohio and moved to Indiana to live with her sister on a farm near the Marshalls' home. Martha was known for her wit and humor, as her son later would be. Martha and Daniel met and married in 1848.