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If the UK Labour party had gone the way of other European socialist parties and not elected Jeremy Corbyn, it would by now be in electoral oblivion. Look at the SPD in Germany, until recently still dominated by Schröderites like Nahles and Scholz, or the Parti Socialiste. Both have haemorrhaged support in recent years. (There are obviously some differences around FPTP, which obviously benefits the two major parties, but still.)
'New Labour' was supported by the establishment ('support' from Rupert Murdoch! Thatcher: 'Tony Blair won't let Britain down.'!) because it had subverted Labour and wanted the inevitable change of government without any policies that would adequately balance out what the Tories had done in the 80s and 90s. Corbyn has been attacked absolutely relentlessly and he's still in there with a fighting chance. (I'm not optimistic about the election, though.)
In the last 40 years all the elections have been won by the Conservatives or Tony Blair. I support Corbyn, but I'm also not mental, so never thought he'd win. But with the chaotic nature of the Tories I'd wager a centrist Labour party led by the likes of Chuka Umunna, or someone else from that now non-existent wing of Labour, would be heading No. 10.