We know Hillary Clinton set a trap for Donald Trump during last Monday's presidential debate. She recalled a time years ago when he humiliated a teenaged beauty queen. He began the week confirming the charge. On Tuesday, he again fat-shamed Alicia Machado on Fox News. On Friday, he implored us to watch her fictional sex-tape.

But there was another trap – only now are we seeing it.

During the debate, Clinton appealed to white working-class voters, many of whom support Trump. Clinton and her husband came from humble beginnings, she said, and they earned their millions honestly. Trump, on the other hand, inherited his fortune, she said, founding his real estate empire on a "small" $14 million loan from his dad.

She went a step further. Clinton questioned whether Trump is worth the billions he says he's worth, and if he is, to prove it by releasing his tax returns. For good measure, she added that Trump has amassed his riches on the backs of hard-working Americans, people like small business owner and curtain-maker Hugh Rodham, her dad.

"I'm really glad my dad never had a contract with Donald Trump," she said, referring to reports in which Donald Trump stiffed contractors. Some went out of business as a result.

Editorial Cartoons on the 2016 Presidential Elections View All 596 Images

Portraying Trump as misogynist is one thing. Having Trump confirm the charge over a period of days is another. You can't buy that.

Portraying him as an out-of-touch 1 percenter is one thing. Having The New York Times report, as it did Saturday, that he may have avoided paying income taxes for nearly two decades due to a massive nearly $1 billion operating loss in 1995; and due to Trump's access to a provision of the Internal Revenue Code that the Times said is "prized by America’s dynastic families" – well, you can't buy that either.

In little more than a week, Hillary Clinton has gone from being a disliked candidate who does not represent the intolerance of America's past (the anti-Trump) to being the candidate, who, as a woman, represents the aspirations of a America's future.

"The suggestion that Fred Trump made Donald really seems to unsettled him," David Axelrod, President Obama's former top adviser, told Politico hours after the debate. "They are in his head."

Expect Trump's meltdown to accelerate this week.

Important here is identifying whom Clinton is targeting. Plenty is known about the role of suburban white women in this election. They are being called 2016's swing voters. But there is another bloc that could swing the election. They are voters Clinton is now trying to reach.

These are white working-class voters.

That may sound absurd. The conventional wisdom is that Trump has a lock on non-college educated whites, especially men. But like any voting bloc, working class-whites aren't monolithic. They are complex, and those complexities help us understand what's really happening.

We don't hear a lot about Clinton's white working-class support because most of her base of power comes from the so-called Obama coalition – minorities, women and white liberals. Add to that the foreign policy faction of the Republican Party. Add too the support of what I'll call the Rotary Club Set, voters whose interests are represented by the editorials of dailies in large Midwestern cities.

Fact is, the Democrats still enjoy a sizable percentage of the working-class support, especially in deindustrializing Rust Belt states like Ohio, where the president won 41 percent of the white working-class vote in 2012. During the primaries, Clinton and Bernie Sanders together won 31 percent of that vote. That's not as good as Obama, but perhaps good enough given that she is ahead of Obama with college educated suburban whites, 57 percent to 46 percent.

There's room to grow in the 10-point differential between what Obama had and Clinton could have. It's doable. Here's why.

First, much depends on what we mean by "working class."

In six states during the Republican primaries, exit polls showed that no one voting for any of the GOP candidates earned less than $50,000 a year. In 18 states, exit polling showed that no one voting for a Republican candidate earned less than $30,000 a year.

"Working class" is often defined by educational attainment and income. Even if these Republican voters did not have college diplomas, they were earning as much or more than the national annual average, which was about $44,500 in 2014.

That alone should cast doubt on Trump's "white working-class" support. It should challenge also the argument that he's riding a wave of populist anger of disaffected Americans left behind by free-trade agreements and globalization. That may be true, but only party true. As someone smarter than I am once said, Trump's power comes equally from the cultural resentments of the petit bourgeoisie.

Which brings to me to voters Clinton can't reach.

She is not going to reach working-class whites trapped in the closed-circuit faux reality of conservative media. She's also not going to reach Democrats who have voted for Republicans since Ronald Reagan but who have not bothered the switch parties.

These people are Trump's people. No contest.

But there is a third subgroup identified years ago by the AFL-CIO. This group, the AFL-CIO found, is more likely to stay home than support a "populist" candidate like Trump. It is pragmatic and commonsensical, and it may be receptive to the ideas of a serious candidate who came from humble origins, who has worked hard to succeed and has revealed the source of her wealth by releasing her tax returns.

This is a relatively small group of voters, but the 10 points it may yield may be all Clinton needs. She has Obama's voters along with Republicans worried about foreign policy, especially about America's relationship with Israel, and along with "local notables" who seek stability in order to get on with business as usual. That alone would be sufficient to get past the post first, but with working-class support on par with Obama's, she's building her own Midwest firewall.