Fed up with a president who compared himself to Jesus, who proposed hanging two political rivals, and then scoffed “I don’t care about my dignity,” the Republican-dominated House of Representatives approved an impeachment resolution, 126 to 47.

The year was 1868.

But when it came time to vote to convict in the Senate, Edmund G. Ross of Kansas—a fellow Republican, veteran of the Union army, and anti-slavery publisher—cast the decisive “not guilty” vote that kept President Andrew Johnson in office.

The vote on June 6, 1868 set off a national uproar. Overnight, Ross became America’s most hated man. Millions cursed him for signing “the death warrant of his country’s liberty.” A hometown newspaper blasted this “poor, pitiful, shriveled wretch, with a soul so small that a little pelf would outweigh all things else that dignify or ennoble manhood.” Ross endured death threats and subsequently lost his Senate seat at the next election.

But over the course of a century, Ross and his vote became an American legend—so much so that John F. Kennedy featured him in Profiles in Courage. By the late 20th century, Ross was portrayed as a politician whose motives were pure, his influence outsized, his suffering Christ-like. Schoolchildren learned that Ross sacrificed his career and his partisan standing with his Radical Republican friends to uphold truth, justice, and the Constitution’s separation of powers.

So what were Edmund G. Ross’s real motives? And did impeachment really hinge on his shoulders alone? Well, the history is messy.

It’s worth remembering today how disunited the United States were in 1868. Slavery had so wrenched the country apart, that 750,000 Americans died fighting over whether to stay together. Shortly after the Union won that terrible Civil War in 1865, John Wilkes Booth murdered Abraham Lincoln, depriving America of the one leader who might have healed the nation.

As Lincoln’s successor, Johnson was an unknown, non-slaveholding Southern Democrat suddenly leading a Republican administration. Even before Lincoln’s assassination, rivals sneered that this illiterate “Reb”—a mere tailor by trade —was a drunk: a supposedly steadying shot of liquor, or three, he took before entering the Senate on Inauguration Day 1865, made him ramble. As president, he stumbled politically, repeatedly, aggressively defending policies Radical Republicans found too merciful.

Still, Johnson was sloppy, not sinister. He tried re-integrating 11 states back into the Union with Lincoln-esque “malice toward none.” But facing vengeful Radical Republicans who dominated Congress, the Tennessee outsider president lacked Lincoln’s war-winning credibility.

The tensions between the angry congressional leaders seeking to punish the South and the awkward president trying to heal the nation ultimately centered on the president’s executive power to hire and fire.

In 1867, the Radical Republicans passed the Tenure of Office Act, overriding President Johnson’s veto. That law prevented the president from firing members of his own Cabinet without Senate approval. Correctly dismissing the law as unconstitutional, Johnson fired one of his harshest critics, Secretary of War Edwin Stanton, a Radical Republican ally. Furious, the congressional Radical Republicans rammed through impeachment proceedings.

On Feb. 24, 1868, the House of Representatives impeached Johnson. Nine of the 11 counts accused Johnson of violating the Tenure of Office Act.

The vote then headed to the Senate, where Republicans needed a two-thirds supermajority to convict Johnson and remove him from office. At that time, Republicans controlled more than two-thirds of the seats . With no pretense of nonpartisanship, a mass lobbying effort bullied any wavering senators to stick to the party line.

While six Republican Senators publicly refused to support the impeachment, a seventh, Edmund Ross, stayed silent. The Radical Republicans simply assumed that Ross, Kansas’s junior senator, would vote with them. Born in Ohio in 1826, Ross trained as a printer because his father deemed him too frail to farm. Arriving in Topeka via covered wagon in 1856, Ross was an abolitionist who led the “Free State” movement opposing the institution of slavery in Kansas.

After fighting his way up to major during the Civil War, Ross started editing the Kansas Tribune. In 1866, the abuse heaped on Ross’s friend, Senator Jim Lane—a Republican who occasionally supported Johnson—turned deadly. Lane shot himself. Another wartime buddy, Governor Samuel Crawford, appointed Ross to be a loyal partisan.

Ross followed orders, initially. But as impeachment loomed, Ross feared that the Radicals were setting a dangerous precedent. Impeachment wasn’t a partisan pistol targeting presidents some dislike, he cautioned, but a punishment of last resort to penalize crimes we all abhor.

“For the first time in the history of the government, the President of the United States was at the bar of the Senate,” Ross later wrote. Removing him “would have practically revolutionized our splendid political fabric into a partisan Congressional autocracy. A political tragedy was imminent.”

The Republicans’ biased trial of Johnson further alienated Ross. Still “opposed to Mr. Johnson” but playing juror not partisan, Ross insisted: “He shall have as fair a trial as an accused man ever had on this earth.” Ross ultimately found the “foundations of the Impeachment… too slender,” and voted to not impeach—leaving the Republicans shy of their super-majority by one single vote.

The skewering of Ross began. Many who tried wooing him before the vote now trashed him. Thugs tried to kidnap him. Investigators threatened political disgrace. Gossips claimed Johnson’s supporters established a $150,000 slush fund to woo him and unleashed an 18-year-old sculptress, Vinnie Ream, to seduce him. Nasty articles sneered that this married father of seven “took his pleasures, not by the quart as drunkards do, but rather by the Ream.”

Still, Ross concluded: “THAT ESSENTIAL INGREDIENT OF JUDICIAL FAIRNESS WAS NOT SHOWN TO MR. JOHNSON... It was an ill-disguised and malevolent partisan prosecution.” Championing the separation of powers, the senator defended the “dignity” of the “Chief Magistrate” and the presidency’s “Constitutional rank as a co-ordinate department of the Government.”

Ross later wrote: “I almost literally looked down into my open grave. Friendships, position, fortune, everything that makes life desirable to an ambitious man were about to be swept away by the breath of my mouth, perhaps forever.” Still, as he announced his dissent on the Senate floor, he thought: “Millions of men cursing me today will bless me tomorrow for having saved the country from the greatest peril through which it has ever passed, though none but God can ever know the struggle it had cost me.”

Actually, Ross was one of “seven martyrs,” Republicans who opposed removing Johnson from office. At least four other senators would have voted to acquit—but didn’t have to, thanks to Ross. Still, this rookie’s surprising vote on May 16, 1868, doomed the impeachment, making him the lightning rod. Three days later, Navy Secretary Gideon Welles observed: “Ross is abused most.”

Senators froze Ross out in the halls. Kansas Supreme Court Justice L.D. Bailey telegrammed Ross: “the rope with which Judas Iscariot hanged himself is lost, but Jim Lane’s pistol is at your service.” Calling him a “coward,” a “sneak,” the Leavenworth Conservative proclaimed: “He is dead—dead to honor, dead to liberty, dead to Kansas.”

One night at dinner, while reading an encouraging letter from his wife, who was at home in Kansas, Ross started sobbing.

Still, behind his high-minded statements defending the separation of powers, Ross was as patronage-driven as any politician. With the vice presidency vacant since Johnson succeeded Lincoln, the greedy, corrupt president pro tempore of the Senate, Benjamin Wade, was set to succeed Johnson. A Wade presidency would have boosted Ross’s rival, Kansas’s senior Senator Samuel Pomeroy. And while there was no evidence Ross was bribed to vote to save Johnson, by June 6 of the same year, Ross demanded that the president he saved now serve him—by appointing his buddy as Southern superintendent of Indian affairs. President Johnson agreed to this —and to future demands too.

Edmund Ross did what politicians do. The regularized corruption of daily politics involves backscratching. While Ross and his six fellow martyrs failed to get re-elected, Democrats did well overall in the 1870 elections. Ross returned to publishing. From 1885 to 1889, he governed the New Mexico territory as an honest reformer.

Ross shouldn’t be demonized or deified. He showed judge-like impartiality in what the Constitution conceives of as a “trial.” He demonstrated courage amid soul-crushing abuse. And he understood that impeachment should not be a losing partisan’s first instinct but the statesman’s last resort: that it should never mean “I hate the president,” only “the president committed a crime.” Impeachment makes sense, Ross said, “only in the gravest emergencies and for causes so clearly manifest as to preclude the possibility of partisan divisions or partisan judgments thereon.”