The 86th New York State Legislature, consisting of the New York State Senate and the New York State Assembly, met from January 6 to April 25, 1863, during the first year of Horatio Seymour's second tenure as Governor of New York, in Albany.

Under the provisions of the New York Constitution of 1846, 32 Senators and 128 assemblymen were elected in single-seat districts; senators for a two-year term, assemblymen for a one-year term. The senatorial districts were made up of entire counties, except New York County (four districts) and Kings County (two districts). The Assembly districts were made up of entire towns, or city wards, forming a contiguous area, all within the same county.

At this time there were two major political parties: the Republican Party and the Democratic Party. The Democrats split over the civil war issue. The "War Democrats" and the Republicans formed a coalition known as the "Republican Union," and supported President Abraham Lincoln and the Union Army's war effort; the rump Democratic Party opposed the war, favoring a compromise with the South, and became known as "Peace Democrats" or "Copperheads." The Constitutional Union (consisting of former "Silver Gray" Whigs and Know Nothings) held a state convention and joined the Peace Democrats.

The New York state election, 1862 was held on November 4. With a large contingent of soldiers at the Civil War front, who did not vote at the state election, surprisingly all five statewide elective offices up for election were carried by the Democrats, including Gov. Horatio Seymour and Lt. Gov. David R. Floyd-Jones. The approximate party strength at this election, expressed by the vote for Governor, was: Democrats/Constitutional Union 307,000; Republican Union 296,000.

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