It plays with the electorate if you push it, but it's almost impossible to push it successfully without being accused of trying to politicise people's deaths. The reason people won't vote Corbyn, though, is not because he's a terrorist sympathiser (although he is), but because he's Jeremy Corbyn. There might be people who'll say to a pollster they'll vote for him, but when it comes to putting a tick in a box, it won't happen.