At this point, polling isn’t really relevant. There is no reality where Trump gets out-campaigned slowly over time. He’s the nominee unless a black swan event derails him. If that were to happen, it would change the dynamics so fundamentally that it would basically start the primary from scratch. It’d be similar to the Dem primary after Hillary lost, where there was a more or less open race because everyone thought they’d be running Hillary again as an incumbent.

Best of luck to the stragglers, though. Might as well be prepared in the event that Trump has to drop out of the race.