Who was the first candidate of the anti-slavery Republican Party?

The first candidate of the anti-slavery Republican Party was John C. Frémont. He ran for president in 1856 and was significant in that election as he represented the new Republican Party, which had formed in opposition to the extension of slavery into the territories of the United States. Frémont's candidacy marked a pivotal moment in American politics, showcasing the party's commitment to opposing slavery and appealing to a coalition of former Whigs, Free Soilers, and anti-slavery Democrats. His platform resonated with many who were increasingly concerned about the expansion of slavery, setting the stage for the eventual rise of the Republican Party as a dominant political force in the years leading up to the Civil War.