Well, this is the question I posed earlier on...is this a major division, a major shift? If Trump does form a splinter party, would his cult sustain with no actual power - or any real prospect of power - behind it? How much of the allure was "doing anything we want" ? I don't think Trump can thrive in opposition because he's absolutely useless at explaining why he thinks something is bad or inappropriate without falling back on waffle and lies.
But - how much a splinter needs to come off to make a long term difference? A few planks? A couple of hundred miles of useless border fencing? I wouldn't be able to quantify it.