there is a limited amount of free-float which you can borrow against. the counter-party needs to purchase that stock, and if a large number of investors want to

there is a limited amount of free-float which you can borrow against. the counter-party needs to purchase that stock, and if a large number of investors want to short sell the stock, they are indirectly increasing the demand. a good example is how hedge funds lost eur30bn back in 2008 trying to short sell overvalued volkswagen stock. i.e. Porsche selling part of its VW stake to ease a short-squeeze