That, too, depends on how one asks the question, and yes, some phrasings bring in Dems and election-deniers answering the same way for different reasons. But since this particular poll has it as a concern for Democrats specifically, I assume the question was phrased along the lines of "are you concerned about the events of January 6?"
Ah, it was "what is a bigger concern: economy or functioning democracy?" 63% of Democrats and 29% of Republicans say "functioning democracy." So yes, but that lets you factor out the portion who are election deniers.