Surveys show majority U.S. support for a carbon tax. Yet none has been adopted. Why? We study two failed carbon tax initiatives in Washington State in 2016 and 2018. Using a difference-in-differences approach, we show that Washington’s real-world campaigns reduced support by 20 percentage points. Resistance to higher energy prices can explain the median voter’s rejection, while ideology explains 90% of the variation in votes across precincts. The 2016 revenue-neutral bill did better with conservatives, while the 2018 green spending bill did better with liberals. Yet we forecast both bills would fail in other states, demonstrating that surveys are over-optimistic.