Not so long ago, cap-and-trade mechanisms for environmental protection were popular in Congress. Now, such mechanisms are denigrated. What happened? This column tells the sordid tale of how conservatives in Congress who once supported cap and trade now lambast climate change legislation as ‘cap-and-tax’. Ironically, conservatives are choosing to demonise their own market-based creation. The successful conservative campaign that disparaged cap-and-trade means it may now be politically impossible to promote it in the US. The good news? Elsewhere, cap and trade is now a proven, viable option for tackling large-scale environmental problems.