In the months after the Senate debate on the amendment, partisan lines on slavery, which already had begun to totter, seemed ready to crumble completely. In the New York legislature, for example, it was not a Republican but a Democrat, Carolan O'Brien Bryant, who sponsored a resolution instructing New York congressmen to back the antislavery amendment. Although many other state legislatures already had adopted similar resolutions, some Democrats in the New York Assembly, especially those belonging to Fernando Wood's “Mozart Hall” organization, refused to budge on slavery. One of Wood's men jabbed at Bryant by asking him what party he belonged to. Bryant shouted back, “Not to the rumhole, Copperhead party, at any rate.” The assembly broke into tumultuous applause. It was strange enough that a Democrat sponsored the amendment, and stranger still that he called his fellow Democrats by the derisive “Copperhead” label created by Republicans.

The incident revealed the unsteady state of politics, slavery, and the constitutional amendment. The Democratic party was badly split, and the Republicans were becoming increasingly so. The Republicans in the Senate had all voted for the measure, but some radical members of the party preferred an antislavery measure that explicitly granted equal rights to African Americans. Democrats in the meantime still struggled with the party's traditional stance against emancipation. As the reaction to Bryant's proposal in the New York Assembly had demonstrated, many Democrats still refused to back down on slavery.