Which we're getting close to. His Republican approvals are close to Dubya's right before the death spiral. I think the Trump presidency is going to play out like Bush's second term.
I would honestly say, even with Trump's approvals in the toilet right now (and basically his entire presidency to date), we're probably still a year away from the point when Republicans start putting more and more distance between themselves and Trump. I think the midterms and the possibility of a primary challenger in 2019 will exacerbate that divide. I don't think there will be any serious abandonment of Trump this year, no matter what Russia dirt is dug up next, simply because he still has value as someone who can rubberstamp their terrible bills right now.