Come on guys, there's no need to lose your heads over this. I don't think running on a policy of "IF everything has gone to pot and Britain is a dystopian wasteland in 2020 because of Brexit THEN we should try to rejoin the EU" is going to guarantee a landslide for the tories. Smith is by no means a great candidate, but it's not like he just announced Labour should campaign in favour of murdering kittens.
Anyway this pretty sums up my view of this election:
I really Don't understand why Smith (or Tim Farron for that matter) thinks that doubling down on Europe is a good move. Fair enough that 75% of Labour voters voted Remain, but what about the millions that they've lost to Ukip, the Tories and not voting in the GE that (according to the media narrative at least) were the bedrock of the Leave vote?
I think doubling down on Europe make sense for both Smith and Farron, especially when you remember that both are not in positions of strength and so have to, to some extent, gamble.
For Smith the important thing to note is that he's running for Labour leadership, not as a general election candidate, so he needs to appeal to members of the labour party, who are likely far more pro europe than labour supporters. And, just, as importantly, Corbyn is pretty blatantly a eurosceptic, so it's something, probably the one thing, that he can use to drive a wedge between Corbyn's base and Corbyn.
For Farron a victory for the Lib Dems at the moment is just making it into the news, and having a strong pro europe position did, at least, do that. And the Lib Dems have such a low base that getting a segment of the electorate behind them, even the relatively small europhile segment, is an improvement and a good thing. This stance may very well help them win in places like Cambridge, for instance.
The other thing to remember, and it must constantly be remembered, to avoid falling into hot takes about, for instance, support for independence, is that Brexit hasn't actually happened yet. Nothing has actually changed since the night of the referendum, so of course a strongly pro EU stance is unpopular now. The europhile stances of Sturgeon, Farron and Smith are, in a sense, a gamble that Brexit will happen and be a disaster (which, tbh, looks like quite a safe bet), so that they can ride in 2020 or whenever and run on a platform of "I told you so. Look what I was saying at the time."