Given the extent of Russia bio and chemical weaponry programs, I would think it quite plausible that the Russian president might seek to escalate with these too

Given the extent of Russia bio and chemical weaponry programs, I would think it quite plausible that the Russian president might seek to escalate with these tools rather than nuclear weapons. Other regimes have gone down the chemical path in the past without immediate or direct repercussions. Their use does not appear to immediately lead to a nuclear response, but they possess the attribute of being one of the most feared weapons in the Russian arsenal.