Im not sure Trump's opposition is so partisan.
Almost Every Republican presidential candidate pre-Trump from the last 30 years is/was anti-Trump: HW Bush, W Bush, John McCain, Mitt Romney
And he's lost some of the loudest conservative voices from the last 40 years: George Will, Peggy Noonan, David Frum, Charles Krauthammer, Bill Kristol...this is a partial list
And dont dare mention all of the Republican officialls involved with Comey/Mueller investigation. They dont qualify in the Trump era either.
Thr Republican party has fallen far from the tree. And it was a pretty ugly tree to begin with.