I've been saying for a while that 2016 will be bad economically, and will most likely result in a Republican victory. If you look back to past Presidential election years, they have been bad in terms of the economy.
Part of the reason (I suspect) that Presidential election years are bad economically is because the president's team that helps cover up the economic problems is looking for new jobs (post-administration), so their attention is focused elsewhere.
As mentioned above, a war could have a big impact - especially if it's in the Middle East. Oil prices will spike, which will help some countries now suffering (Russia, for example).
Good points-thanks.