For his six post-presidential years, Johnson pursued a vindication of earlier setbacks and embarrassments. He had hardly arrived back in Greeneville before he began mapping his strategy to recapture public acclaim. Johnson eschewed the opportunity to compete for the governor's chair and opted instead to set his sights on the prospect of going back to the nation's capital, preferably as a U.S. senator.

Johnson engaged in three separate campaigns, one in 1869, one in 1872, and the final one in 1874-75. In the first, he sought election to the U.S. Senate. At the very last minute the tide went against him in the legislature, and Johnson thereby lost an opportunity to return to Washington only a few months after the end of his presidency.

In 1872, Tennessee stipulated that its new congressional seat would be an at-large one. This suited Johnson, who favored a statewide race. When he could not secure the formal nomination of the state's Democratic party, he declared himself an independent candidate. Although he knew that his actual chances of election were slim, he stayed in the fray. He was determined to break the grip of power which the old Confederates exerted on the Democratic party, and he succeeded. The Republican contender emerged victorious, much as Johnson had calculated, and therefore in a somewhat perverse way this strengthened Johnson's political clout for another day.

That day came in 1874, when he launched hiscampaign for the U.S. Senate. By the time the legislature convened, he was the major contender for the post. But Democratic party successes in the gubernatorial and legislative elections had encouraged a number of other hopefuls. Eventually, the legislature staged fifty-five ballots before Johnson carried the day in late January 1875.

As fate would have it, President Grant summoned a special session of the U.S. Senate to meet in March, enabling Johnson to claim his seat well ahead of the normal schedule. The ex-president strode confidently into the Senate chamber, the scene of his impeachment embarrassment in 1868, and took the oath of office. Many well-wishers, as well as old foes, greeted the battle-scarred political veteran whose vindication had been achieved at last. After lingering in Washington after the close of the Senate session, Johnson returned to Tennessee, where he lived out the short remainder of his days.

With the exception of serious financial reverses and a nearly fatal battle with cholera in 1873, Johnson's sole focus had been his political rehabilitation. Considering his return to the Senate, albeit brief, the argument could be made that he succeeded. But, considering the verdict of most historians, it remains debatable whether he achieved his aims.