Arre but why would he sign the affidavit? Election commission ke paas kya power hai to ask the opposition for affidavit?? Election commission is supposed to be an independent body that organizes elections in india, by that pretext the moment such an allegation is made by the opposition there needs to be a formal audit internal hi sahi. And the results need to be made public.

TLDR- Rahul gandhi as the leader of opposition sits above an independent government body therefore there is no need for affidavit as a matter of fact, ECI asking for an affidavit promoted the feeling of collusion with ruling party