Monmouth does not draw attention to this tightening in its press release, and the MSM apparently hasn't noticed: National poll: Clinton leads Trump by 7, by Nick Gass, POLITICO.com, June 20, 2016.
As before, Trump's problem is not enraged minorities, but a relative weakness among whites, whom he carries 49%-38% (the balance is other candidates/ undecided/ refuse). That's a significant margin, but quite a bit less than the 60% white share achieved by the congressional GOP in the Tea Party year of 2010 and in 2014. It suggests to me, but not apparently to the MSM or Monmouth, that there's precedent to suppose he can do it.