Evidence of Donald Trump’s racism has not been particularly subtle to find for those willing to see it. One could point to moments throughout his pre-presidential life, such as renting discrimination, attacks on the Central Park Five, or his shameful participation in the birther movement. One could look to his policies that disregard the humanity of immigrants and people of color. Or, one could notice a pattern of references to minority populations that assume that they are less important and valuable than whites.

What is it, then, that distinguishes the latest set of tweets from Exhibits A through Y? Last week, the Republican president posted the following to Twitter (three consecutive tweets are concatenated here, but are otherwise unedited):

So interesting to see “Progressive” Democrat Congresswomen, who originally came from countries whose governments are a complete and total catastrophe, the worst, most corrupt and inept anywhere in the world (if they even have a functioning government at all), now loudly and viciously telling the people of the United States, the greatest and most powerful Nation on earth, how our government is to be run. Why don’t they go back and help fix the totally broken and crime infested places from which they came. Then come back and show us how it is done. These places need your help badly, you can’t leave fast enough. I’m sure that Nancy Pelosi would be very happy to quickly work out free travel arrangements!

The difference is that up until now, the racism, though transparent enough, has all been in subtext. Republicans who didn’t subscribe to his hateful messages but still wanted to defend him out of loyalty to Team Red could at least hide behind a veneer of deniability. This is now a thing of the past. Setting aside the fact that the four Congresswomen in question are all United States citizens, and that three of them were born in the United States, telling people to go back where they came from is textbook racism. The U.S. Equal Employment Opportunity Commission even cites “Go back where you came from” as an example of discriminatory language. There’s simply no debate here.

So of course, there’s a debate here, with many of the president’s apologists rushing to explain why his racist tweets aren’t racist. A handful of Republicans have denounced the comments, but not nearly enough. Others have remained conspicuously silent. And my advice for that last group is that they read themselves some Shakespeare. And while that’s usually my advice for everyone, I recommend that these quiet Republicans direct their attention to the Duke of Buckingham.

Buckingham is a character in Shakespeare’s King Richard III. He is based on a real person, but I am going to focus on the character that Shakespeare created. The play follows the journey of Richard, Duke of Gloucester. Richard starts the play fifth in line to the throne, but through a combination of a can-do attitude and a ruthless campaign of cold-blooded murder, he is able to become king. His partner in crime is the Duke of Buckingham, who is willing to support Richard’s heinous treachery in order to ingratiate himself to power.

At one point, Buckingham makes a suggestion that Richard likes, and the latter responds “My other self,” which is the highest praise a narcissist can offer. Richard continues to express appreciation for the support, and tells Buckingham “when I am king, claim thou of me/ The earldom of Hereford,” as a reward.

Richard ultimately becomes king, but it’s not enough. His late brother’s sons are still alive and could one day make a claim to the throne. He brings the issue up to Buckingham, expecting Buckingham to be the one to suggest killing them.

RICHARD
Ah, Buckingham, now do I play the touch,
To try if thou be current gold indeed:
Young Edward lives; think now what I would speak.

BUCKINGHAM
Say on, my loving lord.

RICHARD
Why, Buckingham, I say I would be king.

BUCKINGHAM
Why so you are, my thrice-renownèd lord.

RICHARD
Ha! Am I king? ’Tis so—but Edward lives.

BUCKINGHAM
True, noble prince.

Richard becomes angry that Buckingham seems to no longer be his other self. He expresses his desire to kill the princes. This is a step too far for Buckingham, but he still lacks the courage to stand up to Richard.

RICHARD
O bitter consequence
That Edward still should live “true noble prince”!
Cousin, thou wast not wont to be so dull.
Shall I be plain? I wish the bastards dead,
And I would have it suddenly performed.
What sayst thou now? Speak suddenly. Be brief.

BUCKINGHAM
Your Grace may do your pleasure.

RICHARD
Tut, tut, thou art all ice; thy kindness freezes.
Say, have I thy consent that they shall die?

BUCKINGHAM
Give me some little breath, some pause, dear lord,
Before I positively speak in this.
I will resolve you herein presently.

At this point, an observer notes “The King is angry. See, he gnaws his lip.” Richard wastes no time before finding another lackey to do his dirty work. As for Buckingham, Richard is finished with him.

RICHARD [Aside]
The deep-revolving witty Buckingham
No more shall be the neighbor to my counsels.
Hath he so long held out with me, untired,
And stops he now for breath? Well, be it so.

And that’s all it took, a moment’s hesitation. At this point, all that Buckingham did to put Richard on the throne is forgotten. Only the most recent test of loyalty counts. Richard denies Buckingham the promised and well-earned earldom of Hereford. Buckingham flees. Richard has him captured and executed. So much for him.

And there is a lesson here for those who would defend Trump over the objections of the better angels of their nature. These tweets are not going to be the end of it. It will get worse. So the question you really have to ask yourself is: how far are you willing to go? Because once you hesitate, stop for breath even once, Trump will forget everything you’ve done for him up until that point. The rest of us won’t.

Consider all of the people who are forever tainted with this dark chapter of American history. I’m not talking about people like Stephen Miller, who uses the administration to promote his own white nationalist agenda. I’m talking about people who otherwise might have had distinguished careers, enjoying some kind of public perception of integrity. I’m looking at you, Sean Spicer. I’m looking at you, Sarah Huckabee Sanders. How’s it going, Kellyanne Conway? Everything okay, Lindsey Graham? What’s the first thing you think of when I say “Kirstjen Nielsen”? How will history remember Bill Barr? Who else wants to join the list?

And, literally while I was writing this, our Republican president attacked Representative Elijah Cummings and the city of Baltimore. Are you prepared to take this train all the way to the end? If not, this might be your stop.