Do people who think Le Pen can "because Trump" understand math?

[Vosem]

Obama won Indiana, so this isn't too hard given the right circumstances.

And? Polls of Indiana leading up to the election had Obama and McCain about tied, so I'm not sure what you're getting at?

Polls can change in response to new events.

What is going to cause a 20 point swing in one week?

A major terrorist attack.

I mean, the only clear-cut example of one of these causing a large swing is Spain 2004, and that caused a 7-point swing to the left...

But even that was due to the right stepping in it and their PM-candidate conspiratorially declaring that it was perpetrated by Basque separatists instead of (as it clearly was) Islamists, rather than due to the attack itself. Without some very stupid mistake like that, terrorist attacks that happen during a campaign don't swing elections.