Lib Dems can't do it as they're still toxic to many voters after Clegg. Modest gains off Labour at most.
Labour can't do it because... well... Corbyn.
So nobody can. May can't lose it. It's weird to have an election or vote that you know immediately the result of, beyond any doubt.
Labour's polling has been between 25 and 33% since he is in charge because of the internal opposition, because of the media's ceaseless attacks on him, because they had no clear policies and because in essence it doesn't matter.
This election announcement takes
all of those away - the opposition has to stfu now, the media is legally obliged to provide some balance, Labour policies will be clear for all to see and people will have to choose between voting for her and five years of a Tory government that is willing to do this during the most important negotiations this country has faced in living memory, or voting for someone else.