It really depends on what happens between now and November. Another major terrorist attack in a Western country, especially in the US, would make many undecided voters vote for Trump. I know that's sort of a cable news cliché, but I think it's true.
If things remain more or less as they are today, I think Clinton has a slight edge.
Maybe, but I think it depends on when and where it happens. If it happens within the next 2 - 3 months, then that might be enough time to recover. If it is a small/medium-sized attack in a foreign country, then I doubt any political benefits from that will last longer than a couple months at most. There is a big difference between America getting attacked and some random western country.
I do have to say, though, that the logic in somehow punishing the incumbent's party for an attack that happened to some other country across the world is ridiculously stupid imo. Especially when combined with this silly notion that Republicans are somehow better at handling threats (see: GWB). But, it is what it is I suppose.
Poll
