The president of the United States and his secretary of state were responsible for managing some of the most serious national-security challenges in the world.

But on October 10, 2017, their increasingly strained relationship produced a remarkable public exchange: President Donald Trump suggested that he and Secretary of State Rex Tillerson compare IQ scores—and confidently predicted that he would win.

The challenge followed reports that Tillerson had privately referred to Trump as a “moron.”

Trump initially dismissed the report as “fake news.”

Then he added a challenge.

“I guess we’ll have to compare IQ tests,” Trump told Forbes.

“And I can tell you who is going to win.”

A Remarkable Feud Inside the Administration

Tillerson was hardly an insignificant member of Trump's Cabinet.

The former ExxonMobil chief executive was the nation's top diplomat, responsible for helping manage American relationships with allies and adversaries at a particularly tense moment in international affairs.

North Korea was rapidly advancing its nuclear and missile programs. The Trump administration was reconsidering the Iran nuclear agreement. Relations with Russia remained under intense scrutiny.

Yet the relationship between the president and his secretary of state had deteriorated enough that questions about whether one had called the other a “moron” were dominating headlines.

NBC News had previously reported that Tillerson made the remark after a July meeting at the Pentagon.

Tillerson subsequently held an unusual news conference in which he denied reports that he had considered resigning.

But when directly confronted with the report that he had called Trump a moron, Tillerson did not issue the same unequivocal denial.

Instead, he dismissed the matter as “petty nonsense.”

That left the question hanging over the administration.

Trump's response ensured it wasn't going away.

The President Turns It Into a Competition

During an interview with Forbes, Trump was asked about the reported insult.

Rather than simply dismissing it, Trump transformed the dispute into another competition.

If Tillerson had really called him a moron, Trump suggested, the two men could settle the question by comparing intelligence tests.

Trump already knew who would prevail.

The comment was striking not simply because it involved an argument about intelligence.

This was the president publicly challenging his own secretary of state.

The White House and State Department subsequently attempted to lower the temperature.

State Department spokeswoman Heather Nauert described Tillerson as highly intelligent and pointed to his engineering background. When questioned about Trump's comments, she characterized the president's statement as humor.

“The president is allowed to joke,” she said.

Tillerson, she added, was “more than fine with that.”

“I'm Not Undermining”

The dispute also raised a much more serious question.

Could Tillerson effectively conduct American diplomacy while the president was publicly challenging and contradicting him?

Trump rejected the idea that he was weakening his secretary of state's authority.

On October 10, while meeting former Secretary of State Henry Kissinger at the White House, Trump was asked directly whether his comments had undercut Tillerson.

“No, I didn't undercut anybody,” Trump responded.

But the IQ remark was hardly an isolated incident.

Days earlier, Trump had publicly criticized Tillerson's diplomatic outreach toward North Korea.

After Tillerson revealed that the United States had channels through which it could communicate with Pyongyang, Trump wrote that his secretary of state was “wasting his time” attempting to negotiate with North Korean leader Kim Jong Un.

Trump later told Forbes that publicly criticizing Tillerson did not weaken the secretary's authority.

He argued that it strengthened authority.

Whose authority it strengthened was increasingly obvious.

A Secretary of State Publicly Diminished

The spectacle revealed a deeper problem within Trump's first administration.

Cabinet officials traditionally disagree with presidents behind closed doors. Secretaries of state have clashed with presidents throughout American history.

What was unusual was how publicly the Trump-Tillerson relationship was deteriorating.

Instead of presenting a unified foreign-policy team, Americans and foreign governments were watching the president and his chief diplomat contradict one another in public.

Trump's October 10 IQ challenge turned that dysfunction into something approaching a personal contest.

The question was no longer simply whether Tillerson agreed with the president's policies.

It was whether Trump's own secretary of state privately considered the president a moron—and whether the president could prove that he was smarter.

For the Trump White House, even the relationship between the president and America's chief diplomat had become another contest with a winner and a loser.

And Donald Trump had already announced who he believed the winner would be.