Sen. Bernie Sanders' spokeswoman Briahna Joy Gray implied that former Sen. Claire McCaskill was subtly signaling white supremacists with her post-debate analysis.

McCaskill appeared on NBC News on Tuesday night to analyze the candidates' performances in the first part of the second round of Democratic presidential primary debates.

NBC host Brian Williams set up McCaskill with a question on proposals for job training programs to ease a forced transition from fossil fuels to "green" technology such as solar power. Williams asked McCaskill, a former Democratic senator from Missouri, how voters in the Midwest would react to such policies espoused most notably by Sanders and Massachusetts Sen. Elizabeth Warren.

"It would not be good," McCaskill began. "What I think [Rep. Tim Ryan] is trying to express is a bucket of cold water, which is reality about where America is. America is, generally, not as far along the left line as Bernie and Elizabeth."

Ryan, a moderate candidate in the 2020 Democratic primary for president, pushed back against such a transition during the debate.

“Free stuff from the government does not play well in the Midwest,” McCaskill said.

Gray retweeted a clip of McCaskill's analysis, noting that it sounded like a "racial dog whistle."

"'Free stuff doesn't play in the Midwest' sounds an awful lot like the racial dog whistles about 'hard working whites' vs 'handouts' for POCs and I really hope that’s not what’s happening here," Gray wrote.

[Also read: Bernie Sanders goes after CNN's Tapper: 'Jake, your question is a Republican talking point']