Then, as now, Congress was swept away by rhetorical awe at the historical weight of its deliberations. Then, as now, nobody seemed too sure where the process would lead or what its reverberations might be. In one respect, perhaps, the proceedings have become more civilised: if Bill Clinton believes he has been on the receiving end of unkind jibes from his Congressional adversaries, he can at least be thankful he was spared some of the more colourful epithets hurled at Andrew Johnson.
One Republican House member denounced Johnson as "an ungrateful, despicable, besotted traitorous man - an incubus". The editor of the New York Tribune, Horace Greeley, called him "an aching tooth in the national jaw, a screeching infant in a crowded lecture room". Amid the hysteria, particularly in the course of the House debate, Johnson was accused of dragging the robes of his office through "the purlieus and filth of treason" - and all this just because he had insisted on dismissing his Secretary of War, Edwin Stanton.
Times have changed, of course, and while the rhetoric may have become more polite the issues have changed in weight and importance. Johnson was the man thrust into the presidential limelight after the assassination of Abraham Lincoln. A Democrat and a southerner brought on to Lincoln's Republican ticket in the name of national unity, Johnson had his own ideas how to conduct the reconstruction of the country after the Civil War and his sympathies for former southern slave owners incensed the Republican- dominated Congress.
Stanton became of the focus of his incessant tug-of-war with Congress because Johnson considered him the last key congressional ally left in his cabinet. When he insisted on his removal, Congress rose up in revolt, dug up an old law (subsequently deemed unconstitutional) on Tenure of Office and presented 11 articles of impeachment to the Senate.
The odds looked considerably longer for Johnson than they do for Clinton. Of the 54 senators then sitting, 42 were Republican and only 12 were Democrats. Furthermore, Johnson enjoyed barely a fraction of Clinton's popularity. In his efforts to stay in power, Johnson organised a speaking tour around the country and was heckled relentlessly across the Midwest. "I never saw a man who seemed as friendless and forsaken, and I never felt for any man so much," an unusually sincere Mark Twain wrote for the Chicago Republican.
What saved Johnson was a growing realisation of the absurdity of the charges against him, the possible damage removal from office might do to future presidencies, and misgivings about his putative successor. It came down to the very last vote - that of Senator Edmund Ross of Kansas who eventually sided with the president and was reviled as a perjurer by many of his old friends.
Johnson saw out his full term, but his reputation never recovered. The incident also did considerable damage to the country's political institutions - which, according to Twain, "are not merely food for laughter, they are an entire banquet". Clinton may need to be careful, but the Senate had better watch out, too.