This is great advice, many thanks. Auto-buy is supported by Intrade? So there's no danger of the shares zooming past 6 points before I have a chance to buy them?

Of course the shares could get past 6 and then fall again - in fact they are most likely to - in which case you still lose overall. I'd probably use 9 rather than 6, since the irrational exuberance could conceivably go as high as 6.

If I'd known about this strategy when the right-wing bias on Intrade was rating Biden's chances of stepping down as VP nominee at something like 4%, I would have been a lot more likely to try to profit from it.