In his recent responses to Muslim American Khizr Khan, Donald Trump failed to exercise even a shred of discipline, just as he has failed to do so at many other points in this presidential campaign. Trump could hardly be more helpful to the Hillary campaign if he were cutting it million dollar checks every Monday morning.

I have a soft spot for Trump. He reminds me of my father. My dad was a mailman in the days before mail carts were permitted in Manhattan, so for 37 years he hauled the mail in sacks on his back like a mule to support his wife and children. At the end of the day, when he came home exhausted and sweaty, he wasn’t likely to express political opinions in the language of constitutional rights, legitimate national interest, the common good and limited government. That was supposed to be a candidate’s job. That’s how a democracy works — or is supposed to.

Trump talks a lot like my father did. The problem, of course, is that Trump isn’t walking a mail route. He’s running for president of the United States. It’s intensely frustrating to have Trump as a nominee, because he flips the roles of the leader and the led. In a normal race, a candidate takes the imperfectly articulated wishes of busy, hard-working mailmen and secretaries, teachers and firemen, and sifts them through a filter of moral and Constitutional principles. Then he presents those wishes in purified form, stripped of selfish bias, bad arguments and misinformation.

If voters like what they hear, they adhere to this new, more elevated formula — which has a chance of attracting new supporters to their faction. A candidate does this on issue after issue, in the hope of building a majority consensus around a coherent political platform, which rises to the level of principles you could defend in a friendly argument with someone who disagrees.

On issue after issue, Trump does just the opposite. He reacts to a news event  — like the appointment of a Mexican American judge in his Trump University fraud case — in just the way that a tired, grumpy mailman might react if Jimmy Kimmel stuck a microphone in his face. Trump doesn’t mention that the judge is a member of a La Raza group boycotting Trump’s businesses; he complains that the guy’s parents were Mexicans.

When questioned, Trump doubles down on that reaction because it is his reaction, darn it, and who are you to ask him to betray a stance he took two whole seconds to formulate? Then it’s our job, as conservatives, to take his crude pronouncements, strip them of contaminants, and polish them into something coherent and defensible that could withstand the scrutiny of hostile, biased media. And it’s often possible to do that, because many of Trump’s positions and statements are related to truthful principles, just lazily and sloppily applied.

It’s as if every Republican were now Trump’s media spokesman. This is not supposed to be the voter’s job. And if it keeps up it won’t build an electoral majority, but will saddle us with the scheming, leftist ideologue Hillary Clinton as president. It also might discredit for decades any organized resistance to globalism and multiculturalism in America, which could spell the end of our country.

The most recent case of this ludicrous role reversal came in response to the speech of Khizr Khan at the Democratic National Convention. As you know, Khan’s son was a U.S. soldier who died in the Iraq War, and was posthumously granted the Purple Heart, among other military honors, while Mr. Khan has spoken out publicly on the need for U.S. Muslims to expose any terrorist jihadis in their midst. The DNC chose him cannily: he’s the model American Muslim.

Khan denounced Trump’s proposed restrictions on Muslim immigration into the U.S. In a short but powerful speech, Mr. Khan said that Trump “consistently smears the character of Muslims” and “vows to build walls and ban us from this country.” Then he challenged Trump:

Donald Trump, you are asking Americans to trust you with our future. Let me ask you: Have you even read the U.S. Constitution? I will gladly lend you my copy. In this document, look for the words “liberty” and “equal protection of law.”

Have you ever been to Arlington Cemetery? Go look at the graves of the brave patriots who died defending America — you will see all faiths, genders and ethnicities.

You have sacrificed nothing and no one.

Khan’s appearance was a brilliant piece of political theater, which deserved a subtle response, like George W. Bush’s answer to Cindy Sheehan. Instead, the weary mailman from Queens — sorry, I meant “the Republican nominee for President of the United States of America” — responded in the worst way imaginable short of actual racial slurs.

Trump wondered to reporters why Khan’s wife, the grieving mother of a dead American soldier, had nothing to say — and suggested to George Stephanopoulos, “She probably, maybe she wasn’t allowed to have anything to say.” On Twitter he doubled down, again and again — like an undisciplined teenager addicted to social media — making narcissistic and defensive counterattacks, including the following:

Donald Trump to Army Gold Star father Khizr Khan: “I’ve made a lot of sacrifices” https://t.co/ZOHLGCaOyChttps://t.co/Myp4oyHyX4

— This Week (@ThisWeekABC) July 30, 2016

Remember that Trump avoided the draft during Vietnam. He has joked that avoiding a venereal disease while sleeping around was “my personal Vietnam. I feel like a great and very brave soldier.”

At last, days later, his campaign issued a dignified statement. Of course all this was bloody red meat to the left wing media, which respond to jihadi terror attacks by trying as best they can to hide the killers’ Muslim identities.

Thanks to his reckless responses to Khan, Trump’s entirely reasonable proposal to reduce the number of migrants we take in from countries rife with radical Muslim activists and terrorists could be painted as mindless bigotry — by using the candidate’s own words and actions. All at once, Khan’s pointless invocation of the U.S. Constitution to justify granting First Amendment rights and immigration privileges to foreigners not subject to the U.S. Constitution is irrelevant. Just by way of contrast with what Trump did say, here’s the kind of thing he should have said instead:

Let me thank Mr. and Mrs. Khan for their son’s courageous service. He died defending the U.S. Constitution — whose guarantee of religious freedom for every citizen stands in stark contrast with the way millions of Muslims interpret Islam. To protect that Constitution, we need to carefully vet which potential migrants think like the Khans, and which ones think like the terrorists.

Instead, Trump is dumping on a dead veteran’s family, and even the Veterans of Foreign Wars and Gold Star families are denouncing him, demanding an apology that he is too arrogant to grant. My dad never apologized either. But then he knew better than to run for president.