I think it's time to assume that people who claim that Dolt 45 hasn't said anything racist are simply lying. They know that he's a white nationalist, they are as well, and they simply don't have the courage to say so out loud.
I don't know
Like Captain Swoop, I spend time down the pub with people who consider themselves "salt of the Earth". A very few are openly and proudly racist. Others are like the people quoted in the article, they don't consider themselves racist, they loudly proclaim they aren't racist (a fact they support by noting their friend(s) who are black/brown/yellow) and who get very insulted if you suggest that they may be racist.
They then go on to use the most horrible racial stereotypes, tell very old fashioned jokes in which the race of one or more of the characters is represented as a cruel caricature or make sweeping comments about a country based on lazy generalisations.
It would be easy to say that many of them are a product of the times they were brought up in - British TV in the 70s was institutionally racist - the trouble is that they are teaching this same behaviour to younger generations. They get away with it because there isn't much racial diversity around here.
It seems to be the opposite people that were in denial before are just now starting to say "Wait a minute, he's telling these nonwhite women from the US to go back where they came from. That's kinda racist!" News outlets seem to be abandoning the asinine phrases they often use, like "racially charged" or "controversial", and just saying flat-out "racist". These folks are very late to the party - anyone who was paying attention should have been saying this when he was pushing Birtherism, and only a few journalists are stating the fact that he sounds like David Duke, or one of those buffoons you see on cell phone videos screeching at Hispanic people for speaking to each other in Spanish.
....the thing is, that this doesn't seem to be damaging President Trump or the GOP to any meaningful degree.
Still, the racists, again, know that he represents and advances their own hatred and fear, so they've already been voting for them. People who believe that are against white supremacism have been against him from jump. It's the group I'm describing above that will likely say "Ugh, I'm not voting for this guy again!", particularly if media keeps it up and start treating him like the dangerous, hateful demagogue that he is rather than that wacky rich guy who we all love so much and oh no Hillary's email server!
I'm not sure that there is a large group of people who are shifting away from President Trump. His polling numbers are solid and, if anything, are experiencing a bit of an uptick.
The majority of white people, even those who are a little uncomfortable with the tweets, will still put that to one side come the election and vote Trump/GOP as long as the economy continues to tick along and as long as they feel comfortable financially.