Munsey became directly involved in presidential politics when former President Theodore Roosevelt announced his candidacy to challenge his hand-picked successor President William Taft for the landmark 1912 Republican Party nomination for the presidency. Munsey and George W. Perkins provided the financial backing for Roosevelt's campaign leading up to the Republican National Convention in Chicago. When Roosevelt supporters bolted from the convention, Munsey was one of the most outspoken critics of what were labeled as "corrupt proceedings" and announced that Roosevelt would run at the head of a new party. His encouragement and offer of financial backing led to the formation of the Progressive Party, which acquired the nickname of the "Bull Moose Party" (from TR's quotation that "I'm as strong as a bull moose", when questioned about his age after previously becoming the youngest president upon McKinley's assassination, serving almost two terms as president) then nominated Roosevelt for president. Munsey was one of its most ardent supporters and one of the largest contributors to its "third party" campaign expenses and pulled one of the largest votes ever for a candidate not from one of the two main dominant parties in American history.