You see on the left column where it says "Reconstruction"?
This was the first day of the debates and the very first speaker brought this subject up.
Here is something else you may not know and knowing it will help explain why the subject of black votes came up so early in the debate.
The Joint Committee on Reconstruction
Everything had already been covered in a Joint Committee.
All the Joint Committee was doing was bringing it to the floor.
Don't tell me that everybody in Congress at the time didn't know Section 1 was only for former slaves.
Ark was wrongly decided and it helped seat an unqualified person to the position of POTUS.