Trump's comments coming so close to Super Tuesday, a primary day littered with contests across the deep South, rang alarm bells for some Republicans who saw them as an intentional dog whistle.
"As the guy who is positioning himself as the smartest guy in politics, he sure plays dumb a lot," says Doug Heye, a veteran Republican operative who announced in January he wouldn't support Trump if he was the Republican nominee.
Heye's position has since caught fire in recent days, as the "#NeverTrump" movement has spread across Twitter, with top conservatives, including Nebraska Sen. Ben Sasse, have pledged not to support the nominee.
Trump's history during the primary on inflammatory race issues is one of the top reasons many give for their refusal to support his candidacy. Yet Trump, while never openly courting the fringe groups, has nonetheless garnered their support through his immigration policy proposals and bellicose rhetoric.
In the day since his interview with CNN's Jake Tapper on "State of the Union," Trump has disavowed David Duke, the former KKK Grand Wizard, supporting his campaign. He blamed his refusal to do so Sunday on a bad earpiece, even as he repeated Duke's name multiple times back to Tapper.
But it's more than the most recent dust-up that has some convinced Trump's actions -- or lack thereof -- are intentional.
"Don't tell me he doesn't know who the KKK is," Marco Rubio said at a rally Monday. "We cannot be the party that nominates someone who refuses to condemn white supremacists and the Ku Klux Klan."
Mitt Romney, the 2012 Republican nominee, accused Trump of participating in the "coddling of repugnant bigotry."
"It's clearly intentional," said an operative for a rival campaign, who asked for anonymity to discuss the subject without their candidate's permission. "And it's just so blatant."
The same operative pointed to Trump's 2000 interview where with NBC's Matt Lauer where Trump called Duke "a bigot, a racist, a problem."
"What on earth changed in 16 years? The electoral map, I guess," the operative said.
On Monday, Trump said in an interview with NBC's "Today Show" he didn't "mind disavowing anyone. I disavowed Duke the day before at a major news conference."
For Trump, the support of white supremacists is not a new element of his campaign, but he has never touted associations with the groups or in any way publicly courted their support. Yet his tweets, public comments and answers -- or, in many non-answers -- to questions about the groups have at times served to legitimize efforts of such groups that support him.
In the days before the New Hampshire primary, robocalls touting Trump's campaign were funded by a super PAC affiliated organized by a group, the American Freedom Party, which says it "shares the customs and heritage of the European American people."
Trump's campaign said at the time the candidate "has disavowed all Super PACs offering their support and continues to do so."
How it plays in the polls
Perhaps most notably, any flap related to race -- and there have been plenty -- seems to either bounce off Trump or only galvanize his support. He carries large leads in many of the so-called SEC primary states into Super Tuesday and a new nationwide CNN/ORC survey finds Trump's lead is dominant, and his support tops that of his four remaining opponents combined.
For Republicans like Heye though, the most recent dust-up only serves to raise further concern about the direction a Trump-led GOP, which has grown increasingly more likely in recent weeks, would head.
"It picks at what's been a very, very bad scab for Republicans for a long time," Heye said. "I think the party if they nominate him will be committing an abortion on itself."