It was June 1954, and the Republican personality dominating the new medium of the day—television—was Senator Joseph McCarthy of Wisconsin. After months of venomous cross-examinations, viewers were growing weary of the Senator’s crusade against communist infiltration of American society, and wary that loyal citizens—including some members of the armed forces—were being caught in his crosshairs.

Exasperated by an ad hominem attack on his young law associate Fred Fisher during the Army-McCarthy hearings, Joseph Welch, the general counsel for the Army, delivered the lines above that would mark the beginning of the end of McCarthy’s influence. By the end of July, a resolution of censure against McCarthy was introduced from which the Senator would never recover.

As several of today’s Republican candidates for president face their last chance in tonight’s debate, many doubtless hope to take on Donald Trump by laying a marker worthy of Welch. They will find it difficult: those who have tried to take on Trump so far—Govs. Rick Perry, Jeb Bush and John Kasich—have slumped to single digit support or dropped out of the race. But a few pointers from Welch’s time bear mentioning.

First, Welch had the stuff to fight fire with fire. Though no McCarthy (or Trump), Welch was enough of a showman to have a modest film career a few years later, portraying the judge in Otto Preminger’s 1959 whodunit Anatomy of a Murder. McCarthy himself quipped during the hearings, “Mr. Welch…I get the impression that…you are quite an actor, you play for a laugh.”

Among today’s primary survivors, only Sen. Marco Rubio seems to have a strong enough command of stagecraft and jujitsu to return Trump’s likely attacks with gravity and purpose. He would do well to take after one of Welch’s fine return volleys during the 1954 hearings: “I like to think I’m a gentle man, but your forgiveness will have to come from someone other than me.”

Second, Welch made concessions to certain of McCarthy’s points in order to get to his own. “Senator, may we not drop this? We know he belonged to the Lawyers’ Guild,” he acknowledged, in a reference to Fisher’s youthful indiscretion in joining a leftist organization while in law school. “Let us not assassinate this lad further.”

Virtually every candidate has conceded the appeal of Trump’s core message. But while only Sen. Ted Cruz has succeeded in co-opting Trump’s anti-immigrant momentum so far, there is a third lesson in Welch’s rhetoric: he humanized the victim—“this lad”—thereby setting McCarthy’s callousness in clear relief. “Until this moment, Senator, I think I never really gauged your cruelty, or your recklessness,” he jabbed.

So far, establishment condemnations of Trump’s nativism—most conspicuously, his proposed ban on Muslims traveling to the U.S.—have lacked this personal quality. Although Sen. Lindsay Graham has been more colorful in tone, all leading figures, from Kasich to House Speaker Paul Ryan to former Vice President Dick Cheney, have appealed primarily to abstract principle, not to personal stories.

To understand the limits of appeals to reason, consider the tale of Senator Margaret Chase Smith, a bold early critic of McCarthy. In June 1950, Smith made her “Declaration of Conscience” speech. Speaking just four months—roughly the duration of Trump’s dominance in the polls to date—after McCarthy’s own famous speech declaring “I have here in my hand a list,” Smith combined a partisan attack on “the Democratic administration” with an appeal for restraint.

“The nation sorely needs a Republican victory,” she insisted. “But I don’t want to see the Republican Party ride to political victory on the Four Horsemen of Calumny: Fear, Ignorance, Bigotry and Smear.”

Her courage is notable, and she was right. As the Senate’s own Website notes, during his 1954 spectacle, McCarthy “badgered witnesses while ignoring parliamentary procedures and the rules of common courtesy.” In the end, “Joseph McCarthy fell before the demand of the Senate that its members conform to the body’s rules of comity and civility.” But that was only after “four years of nearly unchallengeable political power.”

To speed his downfall, Trump’s competitors—and critics—would do well to use personal stories instead of reason. They might borrow from former Marine Sergeant Tayyib Rashid. Sgt. Rashid tweeted about his military identification card to Trump, “I’m an American Muslim and I already carry a special ID badge. Where’s yours?”

Hey @realDonaldTrump, I'm an American Muslim and I already carry a special ID badge. Where's yours?#SemperFi#USMC pic.twitter.com/QSf2O9PTi2

— The Muslim Marine🕊 I Stand with Palestine (@MuslimMarine) November 19, 2015

Trump has echoed McCarthy’s affronts at Internet speed. In mere months, he has antagonized military institutions (in the figure of Sen. John McCain), ordinary standards of personal civility (Fox’s Megyn Kelly) and the norms of political discourse (at every turn). But among his supporters, Trump may not be anywhere close to having, in Welch’s words, “done enough”: the most recent poll of Republican-leaning voters puts the world’s most aggressively coifed real estate developer above 40% nationally for the first time.

Trump’s Republican rivals show little capacity to match his charisma, and appeals to reason or conscience have only stoked his outsider status. History suggests that a reversion to the mean is likely to occur only after both stylistic and ideological excesses have been exhausted. But with the Iowa caucuses and the New Hampshire primary less than two months out, time is short. It still feels like early days for Trump. If Welch and Smith are any guide, “at long last” may still be years away.