Wall Street is betting Trump backs down on Iran — but what if the ‘TACO’ trade fails this time?

For six months, markets operated on a repeatable pattern: when tensions with Iran escalated, equities dipped, and investors bought those dips on the assumption that threats would ultimately de-escalate. That assumption became so widely shared that it functioned almost like a trade in itself — often summed up as the "TACO" trade, shorthand for the expectation that the president talks tough and then backs off.

In September, that pattern stopped working. When the usual de-escalation didn't arrive on cue, positions built around the old playbook were left exposed. That matters because crowded, consensus trades tend to unwind quickly when their core assumption breaks — and the resulting moves can be sharper than the original geopolitical news alone would justify.

What to watch now is whether markets reprice this risk more persistently, or treat September as a one-off. Key signals include how equities, oil, and safe-haven assets respond to the next round of headlines, and whether volatility pricing starts to reflect genuine uncertainty rather than a reliably temporary dip.