The continuing Ukrainian crisis has cast a specter over Europe: a natural gas cutoff. Russia supplies 30 percent of Europe's natural gas. In any tit-for-tat exchange of sanctions, this seems the ultimate weapon, dwarfing almost anything Europe and the United States could deploy.
It evokes images of shivering people and shuttered factories. Knowing this, the West will limit sanctions for fear of provoking Russia. Game over. Vladimir Putin wins again.
Maybe not.