The 70% direction-is-wrong thing is more complicated than mere approval/disapproval of D/R policies. It has a lot to do with how various groups of Americans view their own prospects in light of their perception of what affects/will affect them
http://www.mcclatchydc.com/news/politics-government/election/article90664547.html
I say perception because sometimes what is changing is slow to seep into view:
http://www.forbes.com/sites/bobmcteer/2016/09/13/household-income-finally-rising/#3b1b39ab2064
While Mr Obama had about a year of success in  pushing his agenda hard, the Ds in Congress started fighting back and then we have  had years of R obstruction
Congress has "enjoyed" an approval rating of 12-18% for a number of years now, 
Mr Obama did much better- not great but much better than Congress.
Count me in the number who are sick of Congressional infighting and fooling around while we dangle out here in the everyday world .