When it comes to political shocks, it seems the third time's a charm for markets.

Blindsided by the Brexit vote and Donald Trump's surprise election win, traders appear to have learned their lesson, if the reaction to Italy's plebiscite is any guide. One big card in their favor: this time, the polls gave them a heads-up.

While the euro touched a 20-month low in the wake of Prime Minister Matteo Renzi's resignation announcement, the currency has dialed back its slump along with high-yielding currencies. An initial jump in haven assets evaporated. Unlike the U.K. referendum and U.S. vote — when investors and betting markets alike were convinced the establishment side would prevail — this time traders were disabused of such illusions, and it shows. Gauges of equity-market volatility are sliding, as are bets on future swings in the euro.