Blair was indeed little more than a Tory in red rags, but Labour has led most polls this year, almost all from April to July, and Corbyns popularity has continued to grow in working class northern areas from recent polling & tours. It's just whenever there's a leader proposing action on these tax havens, literally every time in British history, the tabloid papers (Who's owners are the largest users of these tax loop holes, with 4 firms owning 71%) absolutely decimate them. Most recently, with Miliband it was latent anti-semitic attacks on him, now with Corbyn whenever he's got a strong lead in the polls they suddenly care about this anti-semitism they whip up? It's so transparent, it's literally always after they announce major policies on tax havens, suddenly they decry the opposition as "unelectable", and it's the craziest, most hilariously blatant self serving prophecy ever.
Let's be honest, whoever leads whichever big opposition party next, if they move to shut down the tax haven loopholes they'll get decimated in a character assassination just like every other one.