In 1899, he ran on the Independent Labor, Republican, and other minor parties', tickets for the New York City Court but was defeated by the Tammany Hall candidate.

In 1901, Seabury ran again for the City Court, this time on the Citizens Union ticket, and was elected to a ten-year term.

Seabury initially ran for a seat on the New York City Board of Aldermen during the 1897 election, but withdrew in order to focus on supporting Henry George's mayoral campaign.

In 1906, he ran again, this time on the Democratic and Independence League fusion ticket headed by Hearst for Governor, and was elected to a fourteen-year term.

On December 8, 1914, Seabury was appointed to the Court of Appeals three weeks before his elective term would begin, to fill the vacancy caused by the death of William B. Hornblower.

Theodore Roosevelt opposed incumbent Governor Charles S. Whitman and convinced Seabury to run in the 1916 gubernatorial election.

Kresel's method relied, instead, on gathering incredible amounts of facts pertaining to the investigation, including bank account documents, brokerage accounts, leases, title records, and income tax returns, and then using these documents to confront a witness during questioning.