As Donald Trump inches closer to the Republican presidential nomination, protests at his speeches are heating up. And with those protests comes hand-wringing about whether the activists targeting Trump are helping him more than they hurt him.

It’s a hard question to answer. Trump has certainly become more popular with Republican primary voters in recent weeks, but he’s also become less popular with the electorate as a whole, so it’s possible that anti-Trump demonstrations may be giving him a boost him in the primaries while damaging him for the general election. It’s also possible that how public opinion on these protests shakes out depends on how they develop — if a protester is badly injured by Trump supporters, say, that could change public perception quickly.

The bottom line is that we just don’t know how these actions are shaping public opinion. We have guesses, but we don’t have data. And in the absence of data, we tend to fall back on analogies and historical precedents.

One such appeal to history came this afternoon from Jonathan Chait, who tweeted that

civil rights protestors had rigorous criteria for justifying civil disobedience. They didn’t try to shut down Goldwater.

I was curious as to whether this was true, so I did what Chait clearly had not — I googled it. More precisely, I did a search of the New York Times’ archives for 1964 on the terms “Goldwater” and “protest.” And it turned up this:

That’s a July 16, 1964 Times article about a demonstration at the Republican National Convention in which twenty civil rights activists were ejected from the floor for disrupting the proceedings in protest of Barry Goldwater’s nomination for president.

And if you read the whole article, you’ll see that the activists, who were members of the Congress on Racial Equality (CORE), a major civil rights organization, used tactics that were essentially identical to those used by Trump’s critics today. They smuggled in a banner. They linked arms. They chanted. They went limp when arrested.

And Barry Goldwater went on to defeat in one of the biggest landslides in American political history.

The Goldwater protest wasn’t unique, either. After I tweeted it, others quickly provided similar cites —  of LBJ supporters jeering Goldwater at a Toledo campaign stop in 1964, and of student activists heckling George Wallace in 1968. The Wallace incident has additional resonance with today, too: According to the newspaper’s account, Wallace supporters assaulted protesters before the candidate even arrived, Wallace himself taunted the activists at the start of his speech, and several protesters were beaten further as they were dragged handcuffed from the venue.

And how did those campaigns work out? Well, like I say, Goldwater was defeated in one of the most devastating landslides in American political history. Wallace steadily declined in the polls as the campaign wore on, failing in his goal of throwing the race to the House of Representatives in order to establish himself as a force to be reckoned with in negotiations over the presidency.

Does this mean that the Trump protests are destined to have a positive effect, or even that the Goldwater and Wallace protests were a good idea? No. But it does serve as a reminder that our memories of past social movements are woefully limited, and that it’s always a bad idea to judge today’s activists by the standards of an invented, sanitized past.

Update | For more on this kind of historical amnesia, see this post from last November, in which I discussed some ways in which criticism of today’s student organizers echoes the rhetoric that was used to attack the civil rights activists of the 1950s.