Part of the ossification of thought about electoral politics comes down to treating the electorate as a fixed group, with each sub-group within it being fixed and equal in size. It's taking for granted who is going to show up and in what numbers, and working only to appeal to the largest share of this group or that group.
So we hear naysayers warn about how, for each blue-collar voter that Trump brings in, he'll alienate two upper-middle class suburban conservadads. That's fine -- the population of blue-collar people is yuge, while country club types are small. If, in order to win half of the entire working class population, he alienates all of the country clubbers, he sweeps the election (perhaps one-quarter of blue-collars would vote Democrat, and the other quarter would stay home).
Trump's "game-changer" has been to turn out a larger share of the population, rather than tweak how well he does with various demographics groups in an electorate that remains the same as before.
We can therefore also ignore innumerate posts like this one from NPR that purports to show why Trump's blue-collar white appeal cannot win elections in 2016, the way it did in 1980. After all, the fraction of the electorate that is white and not college-educated was way down in 2012 compared to 1980.
What didn't occur to this lib-arts major is that the white working class is shrinking within the electorate not for reasons of changing demography. Yes, whites are not as large of a share of the population as they were back in 1980 -- but newsflash: their ethnic replacements do not vote, certainly not at the levels that whites do. Being replaced in the population does not translate automatically into being replaced within the pool of voters.
What actually happened was lower and lower turnout of the white working class over the past several decades. They were between 65-70% likely to go out and vote during the elections of 1972, '76, and '80, but that likelihood has been falling since then, bottoming out around 50% during the 21st century.*
To fix this problem, Trump does not need to take that 50% turnout as a given, and then try to grab larger shares of some other demo (Aztecs, queers, or whoever). He simply has to get the white working class to feel like there's a reason to get out and vote. With dramatically higher turnout of a large group, he doesn't need to obsess over every other little micro-group.
He has been setting records for turnout so far, and Super Tuesday looks to continue that pattern. There will be record turnout in the fall, much of it owing to far higher numbers of white working-class people feeling like they finally have someone who represents their interests (Dems being anti-white, old-guard Republicans being anti-working-class).
This means that Hillary's only possible winning strategy is to suppress white working-class people from voting. They're simply going to be such a tidal wave, and even worse, concentrated in blue states that will turn red (Rust Belt, New England, Mid-Atlantic).
She and Rubio are floating concepts about how Trump isn't truly a friend of the working man, but nobody is buying it. You don't spend tens of millions of your own money in order to regularly stump for a 35% tariff on off-shored manufacturing, if you're aren't truly committed to doing it. Blue-collar folks recognize that he means what he says about bringing good jobs back here through re-negotiating trade treaties, tariffs, etc.
Their only other attacks are weak identity politics stuff (racist, sexist, bla bla bla), which is going nowhere now that the culture war is over.
In short, Trump's victory is all but certain for the nomination and the general, owing to an unstoppable wave of blue-collar whites coming out of the woodwork after having been neglected, abandoned, and disdained for so long now.
* Data from the General Social Survey. White males aged 30-59 with 0-12 years of education.