In an otherwise strong debate performance for Hillary Clinton on Monday night, she stumbled when it came to Iran. In the section of the presidential forum focused on national security issues, she played on a quip Donald Trump made earlier this month about the Iranian Navy's recent maneuvers in the Persian Gulf.
"The other day, I saw Donald saying there were some Iranian sailors on a ship and they were taunting American sailors. 'If they taunted our sailors, I would blow them out of the water' and start another war?" she asked.
The line of attack is understandable. It's part of the #dangerousdonald meme that Democrats and other Trump foes have used now for more than a year. The classic iteration is Clinton's applause line: "A man who can be provoked by a tweet should not have his fingers anywhere near the nuclear codes."
And on its surface it seems like a reasonable criticism. After all, no one wants a shooting war with Iran. And when she puts it like that, it seems like Trump has given yet another example of how he lacks the temperament to be commander in chief.
But Clinton's quip badly misunderstands what's going on right now in the Persian Gulf.
To start, taunting is not the right word for it. Iranian boats have been sailing dangerously close in recent months to U.S. ships that are in the Persian Gulf to secure one of the world's most important shipping lanes. In the first week in September there were three such incidents. In one case, a U.S. boat fired live ammunition to deter the Iranian sailors.
This isn't a hypothetical question either. In January, when two U.S. boats sailed accidentally into Iranian waters, they were boarded by Iran's Navy and crew members were humiliated in a brief incident right before President Barack Obama's final State of the Union speech.
These incidents have so alarmed Gen. Joseph Votel, the commander of U.S. Central Command, that he told reporters this month that he worried about a miscalculation. "If they continue to test us, we are going to respond, and we are going to protect ourselves and our partners."
Clinton presumably wasn't trying to diminish Gen. Votel and the risk he is seeing. A big part of Clinton's pitch to voters on national security is that she understands the world and how it works, whereas Trump is a dangerous amateur who doesn't grasp the basics about everything from the U.S. nuclear posture to our systems of alliances. It would behoove her to take Iran's aggression seriously, and to tell Trump that those are not mere "taunts."
The other problem with Clinton's line about the Persian Gulf incidents is that it undercuts her own pledge to get tougher on the Iranians for their support for terrorism and proxy wars against U.S. allies in the region. Her top national security aide, Jake Sullivan, in June put it like this: "We need to be raising the costs to Iran for its destabilizing behavior and we need to be raising the confidence of our Sunni partners."
One way to raise the costs to Iran is to send the clear message that its provocations in the Persian Gulf will have consequences. In this respect, Trump was correct to threaten Iran, but wrong to be so specific. The substance of his remarks is nonetheless very close to what Votel implied earlier this month. Clinton missed an opportunity to show that she too understood the importance of deterrence in the Persian Gulf.
Eli Lake is a Bloomberg News columnist.