Republican rivals failed to land a successful attack on him in 2016, when he was an unknown quantity politically. Yet this time, he’d be running as a figure with a proven record of pursuing conservative policies, including three Supreme Court appointments.
Trump has instilled such loyalty that he managed to turn John Bolton — who started his career in politics as a volunteer on the Barry Goldwater campaign and who has for decades fought the DC establishment — into some sort of deep state leftist traitor. Anybody who attacks Trump in a primary would be subjected to the Twitter treatment and become a pariah among Republican voters.
Sure, many Republican voters could be sick of Trump’s act in another few years, and worried about risking another defeat.
But that may not matter. As we saw in 2016, if Trump can lock down a solid 25-30% level of support, it would be enough to win the early primaries and drive out all competition, then gaining support in the later primaries. It’s hard to see how anti-Trump Republicans would be able to consolidate around one alternate candidate fast enough.