In Tuesday's testimony by Homeland Security Secretary Kirstjen Nielsen, all the attention was on whether she had heard Donald Trump use a derogatory scatological phrase at a meeting with senators. Overlooked in the coverage was new evidence that when it comes to his favorite proposal, Trump is full of something.
In reference to a border wall, Sen. Patrick Leahy, D-Vt., asked Nielsen about funding: "Have we opened an account that Mexico can put the money in to pay for it?" He persisted in asking whether Mexico would bear the cost as Trump repeatedly pledged. Nielsen had several unhelpful answers, including, "I am not aware" and "How do you mean 'pay,' sir?"
If Mexico had agreed to provide the money, evasive replies would not be needed. But the promise was a fraud, as just about everyone knows by now.
When he talks about the wall, it has never been entirely clear whether Trump is fooling voters, being fooled or both. Never has a politician promised something so emphatically that he has no chance of delivering.
The wall is a bad idea from almost any vantage point. And even if his plan weren't a bad idea, it's an unattainable one. In pushing for it over and over, Trump invites ridicule from critics and disappointment from admirers. Shutting down the government if he doesn't get it, which appears to be a real possibility, would be a perfect way to compound the self-inflicted damage.
His wall fixation is one reason that his stock of admirers has shrunk so much. A new Quinnipiac poll reports that 63 percent of Americans oppose erecting a wall on our southern border.
Republicans are the only group that supports it. "White voters with no college degree are divided with 47 percent supporting The Wall and 49 percent opposed," says Quinnipiac. "Every other party, gender, education, age and racial group opposes The Wall."
Why does Trump continue his Ahab-like quest in spite of the serious political drawbacks? One reason is that he promised it, and he fears that his most loyal supporters will abandon him if he reneges.
That's how he ended up, in a phone call with the president of Mexico last year, practically begging him to play along. "I have to have Mexico pay for the wall," he pleaded. "I have to. I have been talking about it for a two-year period."
What he had been talking about, of course, was that we would build a wall and — this was the cue for thunderous ovations — Mexico would pay for it. But there is no chance that Mexican leaders would ever agree.
A CBS News survey in August found that only 10 percent of Americans think Mexico would pay for the barrier — and only 21 percent of Republicans believe it. His followers know his promise isn't worth a centavo, and they don't seem to care.
Trump has already implicitly admitted defeat. The reason for the impasse over immigration policy is that he demands funding for the wall that Democrats (and some Republicans) are loath to provide. But if Mexico could be coerced into footing the bill, this appropriation would not be needed.
Trump's folly is a boon to economics professors looking for ways to illustrate basic insights. One is the law of diminishing returns. If you own no shoes, acquiring a pair would make your life much better. If you own 20 pairs of shoes, getting a 21st would not. If you have no fencing on the border, putting up 700 miles of it prevents some illegal crossing. But adding another 900 wouldn't make as much of a difference, and the 1,600th mile might have zero additional effect.
As the value of each additional mile falls, the cost would rise, because the most heavily traveled and accessible sites have already been covered. Constructing a high, impenetrable barrier in more remote spots would be more expensive.
Another important economic concept is opportunity cost. If you spend $1,000 on a cruise, you can't spend it on rent. To pay for the wall, Trump's budget proposes to take money from programs that are more useful.
Among the budget items that would get shorted are customs officers, surveillance cameras, coastal interceptor vessels and canine units. The wall wouldn't stop visitors from overstaying visas or prevent drugs from coming via cars, tractor-trailers, tunnels, drones and boats.
What Trump proposes to do is spend $18 billion to erect a giant symbol. What he would really be doing is shoveling money down a — what's the term? — rathole.
Steve Chapman blogs at http://www.chicagotribune.com/news/opinion/chapman. Follow him on Twitter @SteveChapman13 or at https://www.facebook.com/stevechapman13. To find out more about Steve Chapman and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.