Rather than putting his political hopes on hold, Roosevelt ran for a seat in the state senate.[55] The senate district, located in Dutchess, Columbia, and Putnam, was strongly Republican.[56] Roosevelt feared that opposition from Theodore could end his campaign, but Theodore encouraged his candidacy despite their party differences.[53] Acting as his own campaign manager, Roosevelt traveled throughout the senate district via automobile at a time when few could afford a car.[57] Due to his aggressive campaign,[58] his name recognition in the Hudson Valley, and the Democratic landslide in the 1910 United States elections, Roosevelt won a surprising victory.[59]
Despite short legislative sessions, Roosevelt treated his new position as a full-time career.[60] Taking his seat on January 1, 1911, Roosevelt soon became the leader of a group of "Insurgents" in opposition to the Tammany Hall machine that dominated the state Democratic Party. In the 1911 U.S. Senate election, which was determined in a joint session of the New York state legislature,[d] Roosevelt and nineteen other Democrats caused a prolonged deadlock by opposing a series of Tammany-backed candidates. 