 Merritt was a member of the New York State Assembly (St. Lawrence Co., 2nd D.) in 1902, 1903, 1904, 1905, 1906, 1907, 1908, 1909, 1910, 1911 and 1912; and was Majority Leader from 1908 to 1910, Minority Leader in 1911, and Speaker in 1912.He was an alternate delegate to the 1908 Republican National Convention, and a delegate to the 1912 Republican National Convention.He was elected to the 62nd United States Congress, to fill the vacancy caused by the death of George R. Malby, and was elected at the same time to the 63rd United States Congress, holding office from November 5, 1912, until his death on December 4, 1914, in Potsdam, New York.