A native of upstate New York, Parker practiced law in Kingston, New York, before being appointed to the New York Supreme Court and elected to the New York Court of Appeals; he served as Chief Judge of the latter from 1898 to 1904, when he resigned to run for president. In 1904, he defeated liberal publisher William Randolph Hearst for the Democratic Party nomination for President of the United States. In the general election, Parker opposed popular incumbent Republican President Theodore Roosevelt. After a disorganized and ineffective campaign, Parker was defeated by 336 electoral votes to 140, carrying only the traditionally Democratic Solid South. He then returned to practicing law. He managed John A. Dix's successful 1910 campaign for Governor of New York and served as prosecution counsel for the 1913 impeachment of Dix's successor, Governor William Sulzer.
