Although majority of shares sold short were lent by institutions, not all of them were, as some were lent by retail SH.
The above was basis of my
napkin math awhile back in this thread. I should probably update it as it was based on Q1 figures. The bottom line conclusion was that before voting there will need to be recall of 22M shares or a huge 40% of the retail shares (as institutions are not likely to sell before the voting, and, incidentally, based on statistic collected in the research Article I linked above, they are not likely to sell after the voting either. I guess there is caveat here - unless there is major run-up in SP). This potential need to buy shares by short sellers in the quantity equal to 40% of the quantity of retail shares would result in a major event. I believe this was the reason for Elon's 'unwise' tweet.