Andrew Johnson: Hero No More

Benjamin Franklin Butler, Chairman of the House Managers Committee. Known to the South as "Beast Butler."

Karen wants to know how Andrew Johnson survived being impeached.
In a nutshell, bribery and corruption. As you may read in David O. Stewart's book, IMPEACHED: THE TRIAL OF PRESIDENT ANDREW JOHNSON AND THE FIGHT FOR LINCOLN'S LEGACY, there were several slush funds raised by a shady group of men with ties to various sources of shady money, including customs house money, whiskey ring money, money from cheating the Indians (with the blessing of the Bureau of Indian Affairs), and Democratic machine (Boss Tweed, et al.) money. No one has ever traced most of the $100,000 that was raised, but Stewart has done a good job of showing that some of it, at least, most probably went to Senator Edmund Ross, one of the seven Republicans Johnson needed to vote against conviction. Johnson also promoted Ross and his friends after the trial.
Other reasons for votes for Johnson included sympathy for the white South, indifference to the plight of African Americans, concern for the cotton crop should freed slaves become independent farmers, a dislike of President of the Senate pro tem Ben Wade, who would have succeeded Johnson, a complacency based on the certainty of Grant's election ten months after the trial, and a general suspicion of the "extremist" Radical Republicans.