Interesting data from the Economist/Yougov poll:
"The decline in the president’s numbers stems largely from a change among college-educated whites (see chart). These voters will have a disproportionate weight in the upcoming midterm elections to the House of Representatives, both because they show up at polling booths and because so many of them live in marginal congressional districts. In the same poll, 49% of college-educated whites support Democratic candidates for the House (the generic ballot), while 40% support the Republicans. These are awful numbers for Republicans: the president is contagious. Those who are sceptical that Mr Trump’s base of stalwart supporters—the 20-30% of Americans who “strongly approve” of the job he is doing—will ever leave his side are missing the forest for the trees."