The smart view of that is that regardless of whatever ridiculous arguments for Russian imperialism people want to engage in Russia is not physically capable of conquering the Baltic states.
It's debatable whether there is anyone in office in a NATO country who is prepared to use nuclear weapons as a deterrent, or who has sufficient democratic political support to manage or sustain a land war. If China takes Taiwan at the same time, it's mutally beneficial for both Putin and Xi. What leader in NATO can persuasively threaten either Xi or Putin right now, let alone if they acted together?
The responses on this thread haven't really shown a capability for reasoning about the conflicts in economic or abstract terms, which is concerning because as a sample, if an inability to be clear eyed and unblinking about these things is consistent with the view of people in media policy circles, not only is there is a real risk of being blindsided, but it's evidence of a culturally held bias that creates the incentive for these powers to act.
FTFY
Or just used the threat of doing so to take Ukraine piece by piece.
If Russia were to use nuclear weapons in Ukraine, it would be a pariah for centuries, assuming it didn't lead to global thermonuclear war.
This seems to be the case, but no one knows for sure. It's likely that there are people in power who think they can gain an advantage using tactical nukes. Some weapons are specifically designed for this purpose, such as the American ER weapons (PDF) https://www.llnl.gov/sites/www/files/1975.pdf
Chernobyl released ~400 times as much radioactive material into the environment as the Hiroshima bomb. The nuke isotopes are also much shorter lived than what Chernobyl released.