There is no proof of anything until you have an election that contains the whole country. The majority of people who have recently joined Labour are no doubt people who were previously disenfranchised by Miliband, Blair and those years of centrist policy. I don't believe for one second that the country voted by majority for a Tory government and then will suddenly decide to go hard left, of course many Labour voters went to the right on Brexit too.. UKIP is the fastest growing party and will those 3 million people there suddenly decide to vote for Labour? People voted for Brexit on a strong basis of an anti-immigration stance, Corbyn will ensure the floodgates are opened, are 51% going to be happy about that? Are that 51% going to be happy that Corbyn will redirect the defense budget abroad in Foreign Aid....?
I think a lot will be attracted to Corbyn but the greater collective won't be attracted on policy when the Tories will always win on key issues, many underestimate how strong May is going to be on this. The Tories have given people Brexit, 51% of the electorate wanted it and they have taken control now over the process. When Labour can be discredited on the economy so easily are the electorate going to hand Labour the keys to handling what could be the most difficult time our economy has faced... I just cannot see it.
I have yet to hear anyone really say they like Corbyn's policies, most just say he is a 'nice man'.... He will win votes but will that translate into seats, I doubt it. People said the exact same of Farage, he was an honest straight talker yet still we have a Tory government. Corbyn needs to work out how he can win back Scotland first and that is yet another thing that is just not going to happen. Without Scotland he then has to overturn people who voted Tory last time, I was one of them and I don't see any reason why that will change.