No. They have to fail. It's literally physically impossible for them to succeed. If they succeeded, there would be no need to go back in time and do the deed.

I always loved the interpretation of the assassination of Arch Duke Ferdinand that it's a historical event that has been repeatedly meddled with by time-travelers. So many folks want to go back and prevent the First World War and all the subsequent events. So they try to prevent the assassination. However, without the world wars, they would have no reason to go back in time in the first place, so they always fail.

That's what happens if you try and go back in time to change the past. Your actions will always be thwarted, as if reality itself is conspiring against you. Go back to try and kill Hitler? Your gun jams when you try to pull the trigger. The fuse on the bomb fails to go off. Maybe you just have a random heart attack as you're walking through Berlin on the way to intercept him. Maybe the time machine just breaks whenever you try and turn it on. Random fluke events just keep occurring in a way that prevents you from meaningfully changing the past.

And that's why the Archduke Ferdinand assassination is so silly. It's a fixed point in time; you can't go back and prevent it. But so many people have tried that it's now this jumbled mess of an event. Originally it was a simple assassination that worked on the first attempt. But reality kept impinging more and more improbable events that now the assassination is downright comical. People keep trying to prevent the arch duke from being killed, and reality has to invent ever-more ridiculous fluke events to make sure the assassination still happens.