While almost devoid of evil southerners, the House of Representatives was not devoid of Democrats and the Republicans were unable to muster the two-thirds vote that a constitutional amendment requires on their own. When the bill first came up in the House, in June, 1864, only four Democrats voted for it and the vote came up 93-64, less than the required majority.
The election of 1864 were a massive win for Republicans, giving them the numbers they needed and there was no question that they'd pass the amendment when the new congress convened. Lincoln gave a speech to the Congress on December 6, 1864, appealing them to be bipartisan and pass the amendment, pointing out that the election results of a few weeks earlier showed the popular will to end slavery.
That being the case, enough Democrats thought they'd better get on the emancipation train instead of being run over by it and the bill passed. The party split on the final vote was all 86 Republicans, 15 Democrats, 14 Unconditional Unionists, and 4 Union men voting for the amendment and 50 Democrats and 6 Union men voting against.
Delaware and New Jersey both rejected it.
Both overwhelmingly Democrat states.
McClellan barely won Delaware by 3.6%, New Jersey by 6.7%. Of course, McClellan was from New Jersey.
But the Southern voices had been absent since 1861. Amazing that it took almost 5 years to pass an amendment by the federal congress.
Lincoln gave a speech to the Congress on December 6, 1864, appealing them to be bipartisan and pass the amendment.
And on 11 Apr 1865 Lincoln was talking with Gen. Benjamin Butler about his plans to give black Union soldiers a free trip to Panama as a reward for their service.