The horror, the horror. President Barack Obama has put tariffs on Chinese tyres. The sky turns black; two-headed calves are born; famine and deprivation wrack the land. But there might be an upside.

The world's trade economists are as close to unanimous as they get: this is a bad idea. It will do hardly anything to protect jobs, it will make cheap tyres more expensive for poorer Americans and it risks a global arms race of protectionism. The measure does not even pretend the tyres are unfairly priced – it just blocks imports because there have been lots of them.

All true, but only half the story. The conventional wisdom in Washington is that this is a straight trade-off. Placate the labour unions on trade and get them to support Mr Obama on healthcare. Whisper it quietly, and be prepared for accusations of heresy to rain down on your head, but that might be a deal worth making.