I think Nancy Pelosi wouldn't mind losing at all, her job in the party is just to secure big dollar fundraising, and losing in 2020 helps that mission by keeping a clear danger to democracy in power, thus scaring more people into donating more, but I think most of the non-psychopath Democrats and their voters would prefer to win and suffer through a disappointing Biden presidency where we all get to bully Democrats for the next 4 years without Trump to blame.