Final answer:
The final outcome of the congressional campaigns and elections of 1866 was a landslide victory for the Republicans, who gained additional seats in both the House and the Senate. This outcome reflected Northern opinion that the South was unreconstructed and unrepentant.
Step-by-step explanation:
In the congressional campaigns and elections of 1866, the Republicans emerged as the winners. They won by a landslide, gaining an additional 37 seats in the House of Representatives, bringing their total to 173 seats. In the Senate, the Republicans held 57 seats, while the Democrats held 9 seats. This victory gave the Republicans a majority in Congress and signaled that the Northern opinion believed the South was unreconstructed and unrepentant.