Republicans say reopening the FBI investigation is unnecessary because committee members have had the opportunity to question both Kavanaugh and Ford and other potential witnesses have submitted sworn statements.
I think, grammatically, the bold part can be parsed into two ways:
[question] [both Kavanaugh and Ford and other potential witnesses have submitted sworn statements].
[question both Kavanaugh and Ford and other potential witnesses] (who)[have submitted sworn statements].
The second one seems to make more sense to me, although I think the word "who" shouldn't be omitted. If the first one is correct, then I'm not quite sure what it means.
Another thing is that I'm confused about the word usage of 'both'. There are three parties engaged: Kavanaugh, Ford and other potential witnesses, so 'both' might not be suitable as it usually works for two parties. Maybe, the author takes "Kavanaugh and Ford" as one party, and "other potential witnesses" as the other?
The full source.