This is why I place the current conflict so high on the temperature scale. The level of certainty that it will formally spread to nato is increasing. Nato now appears to no longer fear the Russian nuke threats, leaving Putin to issue even shriller threats, and some think he may very well carry it out.
It’s not as though Putin has clearly stated what he would do - he’s made that quite clear. At this juncture NATO leaders should consider he means it.