Johnson escaped conviction by the margin of 35 votes in favor of conviction to 19 against—only one vote shy of the two-thirds majority required for his removal. The shortfall was the result of a last-minute switch by Senator Edmund Ross of Kansas, a recent arrival to Washington who had been appointed to fill a vacated seat. Historian David O. Stewart, however, has found evidence that Ross’ interim appointment was pushed through by his political crony, Perry Fuller, who appears then to have bribed Kansas’ governor with $42,000 to obtain Ross’ reappointment for the remaining four years of his predecessors’ term. The plot thickens at the moment the Senate was about to come to its fateful decision about Johnson’s future. Ross had breakfast with Fuller just before he would join his Republican colleagues to cast their ballots on Capitol Hill. According to Stewart and Mark A. Plummer, there is reason to believe Fuller paid the senator $100,000 on the spot to change his mind, defy his party and vote to acquit Johnson. (This was a huge sum: equivalent to about $15 million today, when adjusted for inflation.)

Despite admirable historical detective work to substantiate these shady dealings, it has proved impossible to find a piece of paper documenting the bribes themselves. (It would have been foolish for Ross and Fuller to provide written evidence of their own guilt.) However, in return for his vote to acquit, Fuller seemingly wanted Ross to get him a high-powered job during the declining days of the Johnson administration. A grateful president indeed appointed Fuller as collector of the Port of New Orleans, in charge of the heavy Mississippi trade between America and foreign countries. Since Congress had recessed for the summer, Ross’ pal assumed office without the need for Senate confirmation—and immediately began to exploit his position to enrich himself and his cronies. Once Fuller was appointed collector, government regulations required him to leave an overwhelming paper-trail that documented his corrupt behavior.

As soon as the Johnson verdict was announced, Republican newspapers were full of charges that Ross’ vote had been purchased. To be sure, American journalism in 1868 was just as politically polarized as it is today. For this reason, the journalistic accounts provided by the leading French newspaper of the day, Les Temps, have a special value. Its readers were much more interested in a biweekly story of 1,000 words of incisive analysis than in passionate partisanship. Moreover, by a remarkable coincidence, the young journalist sending regular dispatches to Les Temps was none other than Georges Clemenceau, who later became one of the greatest prime ministers in French history. His insightful commentaries were translated into English and published in the United States in 1928 as an enduring resource for future historians.

In his account, one of the “most astonishing” features of the Senate vote was Ross’ “sudden and unexpected desertion” of his Republican colleagues. As Clemenceau wrote: “The very day before the vote, Mr. Ross, the senator from Kansas, answered a [Republican] senator who questioned him: ‘Do not worry, I shall be voting on the right side tomorrow.’” As a relatively dispassionate but intensely engaged observer, Clemenceau made it plain that, given his express guarantee to vote to convict the president, Ross’ sudden about-face could not have been motivated by a quixotic repudiation of his long-held Republican principles; it could only be explained by a last-minute sell-out for personal gain.

But for the dirty dealing, the 56 Senators sitting as jurors in 1868 would have convicted Johnson of abuse of executive power despite his lawyer’s claim that such a move was unconstitutional. Once we turn to the two specific charges made against Johnson in the decisive article of impeachment, it becomes even plainer that Dershowitz’s reliance on the precedent of 1868 is misconceived.

Begin with the first of the two charges against Johnson. It asserted that he had “attempted to prevent” the enforcement of a congressional resolution ordering him to allow Edwin Stanton to retain his position as secretary of the Army. The key word here is “attempted.” In fact, Johnson tried, but failed, to discharge Stanton; Stanton refused to obey the president’s order, insisting that he would instead follow the instructions issued from Congress. A similar “attempt” is at the core of the first article of impeachment against Trump. According to witnesses testifying in the House, Trump has made, and continues to make, attempts to coerce Ukraine into an investigation into former Vice President Joe Biden and his son Hunter.

In contrast with Johnson, the articles of impeachment against Trump contend that he actually succeeded in his “attempt” in presidential self-aggrandizement. It is premature to make a final judgment on the matter; this will require hearing further evidence from both sides. Nevertheless, the fact that Johnson might well have been convicted of a failed “attempt” if there had not been corruption provides compelling support for the claim that Trump’s potentially successful “abuse of power,” even if not a crime, is an adequate ground for conviction.

The second charge advanced against Johnson reinforces this point. It attacked him for “unlawfully devising and contriving” to frustrate the implementation of the appropriations act passed by Congress “for the support of the army for the fiscal year ending June 30, 1868.” Similarly, the current House is condemning Trump for preventing “the release of $391 million of United States taxpayer funds that Congress had appropriated,” allegedly in order to coerce Ukraine into an aggressive investigation of a likely opponent in the 2020 election.

Once again, this charge against Trump is even more serious than the one advanced in 1868. While Johnson tried to use congressional appropriations as a weapon in his struggle for control of the army, he did not succeed. In 2020, however, the House already possesses a great deal of credible evidence that Trump succeeded in abusing his fundamental duty to “take care that the laws be faithfully executed.” A failed attempt led to the near removal of Johnson, but Trump seems to have done more than merely make an “attempt.” It is once again imperative for the Senate to hear additional evidence before coming to a decision about whether he succeeded.

Dershowitz has utterly failed in his all-out assault on the broad consensus that presidents can be removed for “abuse of power” even if they have not engaged in blatant violations of the law. The case of abuse against Trump is far stronger than anything that could well have led to Johnson’s conviction in 1868. This means the Senate will soon be facing a moment of truth. If a majority of senators votes to hear witnesses from both sides, they will establish that, regardless of the outcome of the trial, the systematic abuse of power by presidents is impeachable at least in principle, even if their conduct isn’t blatantly illegal. If, however, Majority Leader Mitch McConnell manages to convince 51 senators that the House articles don’t deserve a fair trial, future presidents—of both parties—will predictably use the Senate’s decision as a precedent licensing their own forms of Trumpian abuse.

In casting their ballots, serious Republicans should not allow themselves to be blinded by Dershowitz’s advocacy to the gravity of the decision before them. If they follow McConnell, they will betray the fundamental principle of checks-and-balances that has served as the very foundation of our constitutional republic since the founding.