Complex sentence: The nuclear option has only been used in practice twice (in 2013 and 2017), however the threat to use it dates back at least to 1917, in opinions related to reform of the Senate's filibuster rules.
Split into simpler sentences: The nuclear option has only been used in practice twice. The threat to use it dates back at least to 1917, in opinions related to reform of the Senate's filibuster rules.