[1] The phrase became relevant to the post-American Civil War legal issues surrounding the potential prosecution of former Confederate politicians and officers, as well as questions of enfranchisement of freedmen versus the re-enfranchisement of ex-Confederates.
According to historian Thomas P. Abernethy, "Public office was eagerly sought by the young lawyers and others, and electioneering, unknown in the earlier days, grew rapidly in vogue during the period following 1819.
[5] The Nashville Union newspaper commented on his July 4, 1862 speech, "The sentiment uttered, from the portico of the Capitol last night, by Governor Johnson: 'Treason must be made odious and traitors impoverished,' was a golden sentence.
For example, during Johnson's 1866 electioneering tour, while he was departing his hotel in Cleveland, Ohio for the train, "As his victoria neared the Public Square, he caught sight of a banner stretched between the Forest City House and the Rouse Block reading, 'In the work of reconstruction, traitors must be made to take back seats.'
Announcing that 'government must be fixed on the principles of eternal justice' he went on to declare, that, 'if the man who gave his influence and his means to destroy the government should be permitted to participate in the great work of reorganization, then all the precious blood so freely poured out will have been wantonly spilled, and all our victories go for naught.'
"[15] In 1917 a Utah newspaper that advocated for the federal prosecution (and potential execution) of the Wobblies, resurfaced the phrase, stating, "Old Andrew Johnson did not accomplish much that appealed to the memory of red-blooded Americans, but he did say that 'Treason must be made odious,' and this rule of action is even more applicable today than during the first dark days of the Reconstruction period.
That was ironic, in a way: He had first attracted the support of Republicans as Lincoln's 1864 running mate thanks to his frequent and intense denunciations of his fellow Southern secessionists as traitors who deserved to be strung up, if not killed in combat.