WASHINGTON (MarketWatch) — No one really believes Donald Trump would build a great big wall on the Mexican border if he were elected president.

No one really believes that Bernie Sanders would get free tuition for all public college students, or that Ted Cruz would carpet bomb a Middle Eastern country.

And no one really believes that Hillary Clinton would get tough on the banks, rein in fracking or make any significant fixes to bring down the cost of Obamacare.

This is all campaign rhetoric. At its best, it is aspirational. At its worst, it undermines the credibility and trustworthiness of the candidate.

Clinton, Trump in Strong Positions for Tuesday

Trump came under fire last week after his new campaign guru, Paul Manafort, promised members of the Republican National Committee that the candidate would start acting and sounding more presidential.

“He gets it,” Manafort reportedly said in a closed-door meeting. “The part that he’s been playing is now evolving into the part that you’ve been expecting.”

It sounded a lot like Mitt Romney in 2012 shaking the Etch A Sketch to present a different face in the general election than he did in the primaries.

The remarks prompted New York Times editorialists this week to refer to “The Donald Trump Pygmalion Project,” implying that Trump’s makeover would be as superficial as the one Henry Higgins achieved with Eliza Doolittle.

But it was Charles Koch — the billionaire industrialist, fossil-fuel magnate and climate-change denier — who said it best in an interview this weekend with Politico, averring that he might find it preferable to support Hillary Clinton for president rather than Republican hopefuls Trump or Cruz.

There was only one tiny little proviso: “We would have to believe her actions would have to be quite different than her rhetoric, let me put it that way.”

What, you might ask, could make them believe such a thing?

Perhaps if Clinton ever did release the transcripts of her highly paid talks to Goldman Sachs, the reportedly fawning tone of those remarks might make Charles and his brother David believe her concerns about Wall Street are really just campaign rhetoric designed to neutralize Sanders’s harping on the issue.

Clearly they would prefer a candidate who has consistently shown she knows how to listen to those who give her money rather than billionaire Trump, who doesn’t need their money and listens only to his inner voices, or ideologue Cruz, whose track record is a little bit mixed on this point.

After all, Politico ran a story a year ago when Clinton’s campaign was getting under way with the headline “Clinton’s Wall Street backers: We get it.”

What they got, according to the story, is that all this talk about taming Wall Street is “just politics.” The reporters quoted several hedge-fund managers, mostly anonymously, to the effect that they didn’t believe that Clinton was serious about making them pay more taxes by closing the carried-interest loophole that taxes income as though it were capital gains.

Inequality, sure, that’s an issue. “She’s not saying that a hedge-fund manager shouldn’t be making what they’re making,” an anonymous “leading donor” in the financial sector told the Politico reporters last year. “Just that someone in another job shouldn’t be making 300 times less.”

Who knows, maybe she’ll whittle it down to 299 times less, while she’s getting that remaining 10% of the U.S. population still without health-care coverage into Obamacare so that they, too, can enjoy the benefits of crushingly high deductibles and runaway pharmaceutical prices.

People hear what they want to hear, or, to the extent they follow the mainstream media, what they’re told to pay attention to.

So campaign rhetoric can be very effective.

It allows Hillary Clinton, for instance, to charge in a debate that Sanders cannot give just one example of how campaign money from Wall Street had ever influenced any decision she ever made.

In response to a moderator’s question in this month’s debate in New York, Sanders — inexplicably to his followers — did not cite the widely known example of how Clinton as a senator voted in 2001 against including credit-card debt in individual bankruptcy proceedings, a vital interest to her Wall Street donors.

Then, of course, there is Clinton’s reluctance in the campaign to entertain even rhetorically that big banks — because they are patently too big to fail — simply must be broken up.

Charles Koch, if he took the trouble to follow Clinton’s twisty talk in a Democratic debate last month on how many conditions she would set up for fracking, probably wants to know just how serious she is about reining in a drilling process that has already been voluminously documented as an environmental hazard.

After setting three conditions for fracking to continue — all of which are easier said than done — Clinton concluded: “So by the time we get through all of my conditions, I do not think there will be many places in America where fracking will continue to take place.”

Hmm, maybe, maybe not, Koch is no doubt thinking to himself.

Koch’s remarks to Politico got a lot of media coverage, with commentators pointing out that the billionaire brothers are not as monolithically conservative as you might think, and have even dabbled in libertarianism.

But the Koch brothers really are conservative and ruthless in protecting their business interests, cost society what it may.

What Charles Koch’s remarks suggest is that Hillary Clinton in practice is much closer to these interests than her campaign rhetoric would indicate.

Barring any last-minute upsets or surprises, voters will have to squint very hard come November to determine where rhetoric ends and reality begins in these two likely nominees.