I haven’t read recent surveys, but 30-35% is simply a normal distribution that would be expected from a survey like this — about 1/3rd like him, 1/3rd don’t, and 1/3rd are in flux. Variations in that are what’s significant.
The fact that he hasn’t dipped much below a third I would interpret as normal. After all, Trump dissed a Republican Senate war hero in the crudest terms, and the party still nominated him.
Trump’s strategy is to keep the normal distribution, and expand by lying to the other 2/3rds to peel enough of them away. To work, though, he needs a fractured opposition. Hence, the shock value of trash talk.
It’s a game.
A values-free game. The problem is the rest of the Party.
Trump may be able to diss a military hero, cuddle up to the Russian mob, and root for alt-right racists. I’m not sure the other Republicans can pull off the same thing as they also work to kill Medicare, lower Social Security benefits, and raise taxes. Hugging fascism by aggressive, armed Nazis in our business districts may be one step too far.
No wonder Republican billionaires are looking to build several more propaganda broadcast networks. They’ll need 'em.