Conditional on New START being renewed or replaced by another similar treaty after February 2026, will there be a nuclear exchange between Russia and the US by 2035?

New START is a nuclear arms reduction treaty between the United States and the Russian Federation, which was signed on 8 April 2010. After its extension in 2021 it is expected to last until 5 February 2026.

We ask a pair of questions about the odds of a Russia-US nuclear exchange conditional on New START being renewed/replaced or [conditional it not being renewed/replaced](ADD LINK) in hopes of shedding some light on the impact of the treaty. (But of course differences between forecasts on the two questions could also partly reflect the impact of "third variables" that influence both whether the treaty is renewed/replaced and whether a Russia-US nuclear exchange occurs.)