There’s no real doubt that Melania Trump’s Republican National Convention speech last night was partly plagiarized from Michelle Obama’s Democratic convention speech eight years earlier. The two passages had way too many phrases, in exactly the same order, for the similarities to be a coincidence.

But instead of admitting the obvious, the Trump campaign has dug in its heels, insisting that nothing untoward occurred. "These were common words and values," campaign manager Paul Manafort said on Tuesday. "To think that she'd be cribbing Michelle Obama's words is crazy."

Manafort turned the blame on Hillary Clinton, arguing that the response to Melania’s speech is "an example of when a woman threatens Hillary Clinton, how she seeks out to demean her and take her down."

This has become the Trump campaign’s standard response when it’s caught making a mistake: refuse to admit they’ve made an error no matter how obvious it might seem, and then escalate by blaming everyone except themselves for the misstep. This tactic has often produced poor results for Team Trump, magnifying what could have been minor gaffes into major scandals that consume the media’s attention for days.

But as bad as this never-admit-error policy is as a campaign strategy, it would become even more disastrous if Trump reaches the White House.

Trump denied that an obviously anti-Semitic tweet was anti-Semitic

One egregious example came earlier this month, when Trump tweeted out a photo showing Hillary Clinton’s face next to a six-pointed star and a pile of money. When people pointed out that the graphic came from an anti-Semitic website, the campaign took down the tweet and put up a new version with a circle.

The smart thing to do at this point would have been to just admit that Trump had accidentally and unknowingly retweeted an anti-Semitic image. Instead, the Trump campaign concocted increasingly far-fetched explanations for the star. They argued that the six-sided star could just as easily be seen as a sheriff’s star, and pointed out that Disney had published a book with a red six-sided star on its cover:

Where is the outrage for this Disney book? Is this the 'Star of David' also?

Dishonest media! #Frozen pic.twitter.com/4LJBpSm8xa — Donald J. Trump (@realDonaldTrump) July 7, 2016

Of course, the cover of this Frozen children’s book was not playing on anti-Semitic stereotypes about rich Jews corrupting politicians. It’s unlikely that this defense convinced anyone who wasn’t already firmly in Trump’s camp.

But what Trump’s continued defense did accomplish was to keep the issue in the headlines for another couple of news cycles. The media circus surrounding this issue came at exactly the same time as FBI Director James Comey’s announcement that he would not prosecute Hillary Clinton for mishandling classified information. Comey described Clinton as "extremely careless" — a comment that would have done more damage to Clinton’s reputation if it weren’t overshadowed by the hoopla over Trump’s six-sided star tweet.

Trump refused to admit his campaign manager grabbed a reporter

On March 8, Trump’s then-campaign manager, Corey Lewandowski, grabbed Breitbart News reporter Michelle Fields as she was walking next to Donald Trump. He pulled her hard enough that she had bruises two days later.

While there was some initial dispute about what happened, video evidence soon left no doubt that Lewandowski had, in fact, grabbed Fields. If he had simply admitted to grabbing Fields and apologized, it might have been a one-day story.

Instead, Lewandowski labeled Fields "delusional." "Perhaps she made the story up," Trump said "I think that's what happened," The campaign stuck to this story for weeks, even as more and more evidence emerged that Fields was telling the truth.

This was not a good look for a campaign that has struggled to appeal to women voters. And Trump’s refusal to admit the obvious gave the story a lot more attention.

There are a lot of other examples in the same vein:

After Trump faced tough questioning from Fox News reporter Megyn Kelly at a Republican debate in August 2015, he told CNN that Kelly had asked "all sorts of ridiculous questions. You could see there was blood coming out of her eyes, blood coming out of her wherever." This seemed like an obvious insinuation that Kelly had PMS, but Trump insisted that the "wherever" he had in mind was her nose.

In November 2015, Trump claimed that "I watched in Jersey City, N.J., where thousands and thousands of people were cheering" after the World Trade Center fell on 9/11. Trump wasn’t able to substantiate this accusation, and no one else has been able to find evidence for the claim. But Trump refused to admit that he’d misspoken.

At a February rally, Trump told supporters, "If you see somebody getting ready to throw a tomato, knock the crap out of them. I will pay for the legal fees. I promise." The next month, he said he was looking into paying the legal fees of a man who had sucker-punched a protester at a Trump rally. But when Trump was challenged on his apparent incitement to violence, he insisted that he’d never offered to pay for the man’s legal fees.

A president who refuses to admit mistakes would be a disaster

To see how disastrous this approach to truth-telling could be in the White House, we only have to think about an incident like the accidental US bombing of the Chinese Embassy in Belgrade. That bombing provoked a strong reaction from the Chinese government, forcing President Bill Clinton to admit to the mistake and apologize.

American presidents face crises like this on a regular basis. President Ronald Reagan faced a similar situation in 1988 when the US accidentally shot down an Iranian civilian aircraft. In 2001, in one of George W. Bush’s first foreign policy tests, a US spy plane crashed in China after colliding with a Chinese fighter jet that had been following it. Bush apologized to the Chinese. Reagan never formally apologized to the Iranians, but the two nations ultimately reached a settlement.

Donald Trump’s apparent policy of never admitting mistakes could have terrible consequences in the Oval Office. His behavior on the campaign trail suggests that he would be unlikely to admit mistakes and defuse tense situations. Instead, his first instinct would be to escalate every conflict in an effort to bully foreign adversaries into giving him his way. That might work in some cases. But in others — especially against powerful countries like China or Russia — the results could be disastrous.

And even on the domestic front, Trump’s policy of escalating small gaffes into major scandals means his administration would likely be consumed with endless petty bickering. If Trump has not alienated all of the key congressional leaders by the time he is sworn into the presidency, his tendency to pick unnecessary fights and deny obvious mistakes is sure to poison the well further during his early months in office.

Did Melania Trump plagiarize Michelle Obama?