And the answer is: I'm not sure they ever will.
The reason isn't necessarily that they approve of what he's doing. But think of what it would mean for a Trump partisan to really, truly, turn on him.
It would mean admitting that the people they hate most -- the media, the liberals, the academics, the dreaded "elites" -- they were right. That the Trump backers who thought he'd "drain the swamp" or bring back coal jobs, or tackle the opioid epidemic or whatever it is they believed Trump would do, were hoodwinked. Just like we told them they would be.
That's deeply humiliating, and ultimately, that's the key barrier to Trump's base turning on him.
So I suspect they'll deny it for as long as they can. And they can for a long time. There's nothing that will compel them to come around, of course. Media reports? They're biased! Job losses? Impossible to trace those back to Trump policies; maybe it's liberal sabotage. Criminal indictments? That's the deep state. There will always be an out, or an excuse, or a dodge.
Reckoning with what really happened, admitting that one's mortal enemies had it right all along, well, that would take a pretty big dose of personal responsibility. And we all know how modern conservatives fare on that metric.
"There comes a point in every plot where the victim starts to suspect; and looks back, and sees a trail of events all pointing in a single direction. And when that point comes, Father had explained, the prospect of the loss may seem so unbearable, and admitting themselves tricked may seem so humiliating, that the victim will yet deny the plot, and the game may continue long after."