Sentence:  But though the Southern States , when drafting a constitution to unite themselves , narrowed the difference to this fine point by omitting to assert the right to secede , the fact <WSD>remained</WSD> that by seceding from the Union they had already acted on the concept that it was composed primarily of sovereign states . 
Meaning of the word marked with <WSD> tags:  be left; of persons, questions, problems, results, evidence, etc.