During last week’s climate town halls, several Democratic presidential candidates endorsed a carbon tax. It’s an idea Barack Obama and Hillary Clinton shied away from. At Bloomberg Opinion, I argue they had good reasons for keeping their distance.

A memo for the Clinton campaign estimated that a carbon tax of $42 per ton on greenhouse-gas emissions would raise annual energy costs by $478 for the average household, and by $268 for the poorest fifth of households.

When considering that number, keep in mind another poll finding. In November 2018, the AP-NORC Center for Public Affairs Research ran a survey about climate change that found, in line with other polls, that most Americans believe it is happening and that human activity is causing it. Nearly half of respondents said that recent extreme weather events had influenced their thinking on the issue. But 68 percent opposed paying even $10 extra in their monthly utility bills to address the issue.