Donald Trump and Bernie Sanders are the antithesis of the conventional politician. They are not programmed, their lines are not focus-group tested, and they take positions far outside the mainstream. But the victory speeches they gave in New Hampshire Tuesday night showed they have mastered the oldest political trick of all: promising things they can't deliver.

Trump showed the most chutzpah, conjuring gaudy images of the wonders he will bestow. You name the problem, and he will banish it. "We're going to take care of our vets," he said. "We're going to have strong, incredible borders," he said. Building a wall, he said, is "not even a difficult thing to do."

This 2,000-mile long barrier will stop not only illegal immigration but drug smuggling: "We're going to end it at the southern border. It's going to be over." Noting the prevalence of heroin use in New Hampshire, he said, "We're going to work with you people to help you solve that very big problem and we'll get it done."

The Islamic State? "We're going to knock the hell out of them. And it's going to be done the right way." In every realm, Trump pledged, "we're going to win so much, you are going to be so happy, we are going to make America so great again, maybe greater than ever before."

You may note that the absence of specifics in this shriek of ecstasy. Trump is like a car salesman trying to sell a car that not only hasn't been built but hasn't even been designed, by a company that has never built a car. The buyer isn't even told what kind of vehicle it will be or how much it will cost. Or maybe it's not a car but just some means of transport.

Anyone who tried to get Trump the businessman to approve a project based on such vapor would be promptly evicted. This is not the art of the deal. It's the art of the con.

His website goes into slightly more detail but fails to make his promises look plausible. The Tax Policy Center in Washington says his tax plan, which he bills as revenue-neutral, would cut receipts by 22 percent.

Trump told The New York Times editorial board he would slap a 45 percent tariff on Chinese goods. Many of his supporters would love that, but he later denied saying any such thing, despite recorded proof: "They were wrong. It's The New York Times. They are always wrong." So it's anyone's guess what he would do about China.

Sanders was not to be outdone in promising the moon. He vowed to "make public colleges and universities free," slash student loan debt, "rebuild our crumbling infrastructure, increase Social Security benefits, and "guarantee health care for all" through a single-payer system.

Unlike Trump, he does not shrink from specifics. But, like the poet T.S. Eliot, he evidently thinks that "humankind cannot bear very much reality." So his proposals include a giant heaping of pixie dust.

The tax increases that are supposed to fund "Medicare for all" would not suffice. The bipartisan Committee for a Responsible Federal Budget figures that over 10 years, the revenue would fall $3 trillion short of covering the cost. That's the optimistic view. A more pessimistic estimate comes from economist Kenneth Thorpe of Emory University, who favors a single-payer model. He calculates the gap at $14 trillion over a decade.

Fattening retirement checks would also be expensive, and Sanders wants additional tax increases to pay for them. The resulting rates would be so high as to be not only punitive but economically harmful.

A household whose income exceeds $250,000 would face marginal rates ranging from 62 percent to 77 percent, according to website Vox.com. The maximum rate on capital gains would nearly triple.

Sanders doesn't burden his audiences with the negative effect these enormous tax increases are bound to have on the economy. Even liberal economists acknowledge that high rates discourage work, saving and investment, while fostering wasteful tax dodges.

Nor does he admit that getting them through Congress—even a Democratic Congress, which is unlikely—would be impossible. Everything is supposed to happen through the "political revolution" he sees shimmering on the horizon.

A lot of voters are drawn to these candidates because they are sick of being let down by elected leaders. But if they think Trump or Sanders will redeem their faith, they are in for a big surprise.

© Copyright 2016 by Creators Syndicate Inc.