The NYT does not say that Trump's strongest support group is "reg democrats LEANING voting pub". It says that the level of support for Trump is highest among "SELF-IDENTIFIED REPUBLICANS who nonetheless are registered as Democrats ... a coalition that’s concentrated in the South, Appalachia and the industrial North." In other words, socially conservative white racists who left the democratic party over its support for civil rights.
The article also notes that Trump's pattern of geographic pattern of support corresponds "to a map of the tendency toward racism by region, according to measures like the prevalence of Google searches for racial slurs and racist jokes, or scores on implicit association tests."
You can cherry pick and try to spin it to look like Trump's support is coming from swing voters or NY liberals all you want. But the truth is that Trump is appealing explicitly to people who are motivated by racism and xenophobia. And, on that platform, he is currently running 17 points ahead of anyone else in the GOP primary.