A big question in the days following President Trump’s controversial tweets about four minority congresswomen has been: Why aren’t more Republicans unequivocally denouncing them as racist?

One big reason GOP lawmakers haven’t all labeled Trump’s telling the four representatives — Alexandria Ocasio-Cortez (N.Y.), Ilhan Omar (Minn.), Ayanna Pressley (Mass.) and Rashida Tlaib (Mich.) — to “go back” to the countries they came from as racist is because they know how loyal Trump’s base is. Given this, if they publicly offend him, the president could encourage his supporters to back a more Trump-loyal candidate in the next Republican primary. He did so to several in 2018.

Some Republicans clearly agreed with the sentiments Trump expressed and embraced them. Others did verbal gymnastics to not address the question — House Minority Leader Kevin McCarthy (Calif.) pivoted to frame the debate as about “socialism vs. freedom” rather than race. Some, like Rep. Mike Kelly (Pa.) contorted themselves to the point of redefining other phrases to avoid having to place any blame on Trump.

"You know, they talk about people of color. I’m a person of color. I’m white. I’m an Anglo Saxon. People say things all the time, but I don’t get offended,” Kelly told VICE News. “‘With a name like Mike Kelly you can’t be from any place else but Ireland.’”

But this week also showed how many Republicans vary in how they define or are willing to apply the word “racism.” That’s something Trump’s candidacy and presidency have forced to Republicans explore, publicly. They haven’t always been shy about using the R-word, even when criticizing Trump.

In December 2015, after hearing Trump’s support for banning Muslims from traveling to the United States, Sen. Lindsey O. Graham (R-S.C.), who was running against Trump for the GOP presidential nomination, told Americans: “He’s a race-baiting, xenophobic religious bigot."

Months later, Trump accused a judge presiding over a lawsuit involving his business of having a bias against him because of the judge’s Mexican heritage. Many Republicans remained silent, but then-House Speaker Paul D. Ryan (R-Wis.) criticized the remarks claiming that the judge would be unfair to Trump because he is white as “the textbook definition of a racist comment.”

Now, as president, Trump has had nearly solid Republican support, no matter what he has said, even from some of his most harsh former critics in the GOP.

“A Somali refugee embracing Trump would not have been asked to go back,” said Graham this week, apparently referencing Omar, who fled civil war in Somalia as a child before immigrating to the U.S. “If you’re a racist, you want everybody from Somalia to go back cause they’re black or they’re Muslim.”

And when the House voted this past week to condemn the president’s statements as racist, some Republicans challenged whether the House could even use that label. In the end, only four GOP House members voted to support the resolution.

Before the vote, Rep. Will Hurd (R.-Tex.), the only black Republican in the House, told CNN’s Christiane Amanpour that Trump’s tweets were “racist.”

“I think those tweets are racist, and xenophobic,” he said. “They’re also inaccurate.”

He was joined by Reps. Brian Fitzpatrick (Pa.), Susan Brooks (Ind.) and Fred Upton (Mich.) in backing the resolution. Rep. Justin Amash (Mich.), who quit the GOP this month and became an independent, also voted in favor.

Part of the issue is that what constitutes racist language has changed over time. But to many academics who study the issue, the purpose of racism has been consistent.

Ibram Kendi, director of American University’s Antiracist Center, writes in his forthcoming book “How to Be an Antiracist” that racism is “a powerful collection of racist policies that lead to racial inequity and are substantiated by racist ideas.”

And scholars Karen E. Fields and Barbara J. Fields wrote about racism in “Racecraft: The Soul of Inequality in American Life" that “Racism refers to the theory and the practice of applying a social civic or legal double standard based on ancestry and to the ideology surrounding such a double standard,” they said. “Racism is not an emotion or state of mind, such as intolerance, bigotry, hatred or malevolence.”

“Racism is first and foremost a social practice, which means that it is an action and a rationale for action, or both at once,” they added.

There is of course, a strict dictionary definition of racism (“hatred or intolerance of another race or other races”). Most people in a position of power know that; it’s a matter of where they draw the line on what qualifies as racist, and whether they adjust that line when it’s politically convenient to do so.

While the president did not use any directly derogatory terms in his tweets, he tapped into tropes used in the past to raise anger against minorities. Leaving room for plausible deniability is a good way to give yourself, and your political allies, room to maneuver when you make statements that are racist. As The Fix’s Aaron Blake has written, Trump recognizes the benefit of plausible deniability, and frequently utilizes it.

Republicans seem to be on completely different pages about what constitutes racism. Some even blame the left, saying it is liberals who are increasingly invoking racism and showing intolerance. That argument on its face is not illegitimate. Liberals, especially those of color, would argue that they are more vocal in calling out racism because racism is indeed far-reaching in our society.

Either way, hearing that racism is so prevalent has allowed some Republicans to use claims of its omnipresence as an excuse to neither address it nor even acknowledge it at all.

But even more important than how Republican lawmakers define racism is Trump’s view that whether his tweets are racist or not may be irrelevant.

The day after the president’s original tweets, he was asked his thoughts about the fact that his comments had widely been interpreted as racist. And he replied:

“It doesn’t concern me because many people agree with me. A lot of people love it, by the way.”

He’s right. A lot of people in his base did love it, so much so that at his campaign rally a few days later, Trump supporters began to chant “Send her back!” to display just how much they agreed with his original sentiments.

While the president eventually disavowed the chant that his original comments inspired, he has not apologized for his initial tweets and continues to question the patriotism and loyalty of the congresswomen, vowing Friday to punish them for their language.