The 1903 United States Senate election in New York was held on January 20, 1903, by the New York State Legislature to elect a U.S. Senator (Class 3) to represent the State of New York in the United States Senate.
Republican Thomas C. Platt had been re-elected to this seat in 1897, and his term would expire on March 3, 1903.
At the State election in November 1902, 28 Republicans and 22 Democrats were elected for a two-year term (1903-1904) in the State Senate; and 89 Republicans and 61 Democrats were elected for the session of 1903 to the Assembly. State Senator Patrick F. Trainor who had been re-elected, died on December 25, 1902, and his successor Peter J. Dooling was elected only after the senatorial election, on January 27. The 126th New York State Legislature met from January 6 to April 23, 1903, at Albany, New York.
The Republican caucus met on January 19. 25 State senators and 84 assemblymen attended, and State Senator William W. Armstrong presided. The caucus re-nominated the incumbent U.S. Senator Thomas C. Platt almost unanimously. A single vote was cast for U.S. Secretary of War Elihu Root by Assemblyman William A. Denison, of Jefferson County. Besides Denison voting against Platt, a small number of anti-Platt men did not attend the caucus. Boss Platt had forced the nomination of Attorney General John C. Davies to the New York Supreme Court in the 5th District, against the local Republican organization's wishes who accused Davies of incompetence. Davies was defeated in a landslide by Democrat Watson M. Rogers although the 5th District was heavily Republican. Thus boss Platt's power began to wane.