I'm trying to think of how to explain this so it's as real and solid as a concrete block. It's honestly not complex, and it's not "magic thinking".
Let's imagine that a Republican-dominated (not necessarily conservative-dominated) Congress is faced with a president who's trying to push something similar to 'comprehensive immigration reform' through the legislature.
Some legislators are gonna be fer it, and some are gonna be agin it (for various reasons).
We know which way the treason party's going to come down on such a proposal, but by and large, most Republicans would probably be agin it for reasons of principle, or because they know the voters back home would skin them alive for supporting it.
If the president is a Democrat, then the natural tendency of the Republicans to oppose him along party lines, is a no-brainer. There's no danger in crossing their arms and saying, "no".
On the other hand, what if the president pushing for this is a Republican? Do you really think the Republicans' opposition is going to be nearly as strident or unified? I think you know that it won't be. We already saw this at work during the first six years of the GWB presidency. He gave the libs nearly everything they wanted, and the Republican-dominated Congress almost never stood in his way.
The only way to hold such bad behavior at bay, is if a few hundred thousand angry citizens are right outside the Capitol Building, waving nooses and pitchforks. But how often are such protests going to be organized? Every time the Republicans in Congress might be suspected of possibly caving in to the liberal Republican in the White House?
Pardon me, if I'm just a bit skeptical about our ability to stand watch over Congress to that degree.
So, that's my point, and it's about as clear as I can make it. These are the political dynamics that play out in every administration - Democrat or Republican.
So these ‘staunch conservatives’ manifest when a commie democrat progressive is in the White Hut, but these same people are transmogrified into complacent or even go-along-to-get-along republican dweebs when a liberal republican is in the White House. Got it. ... No magic thinking there, no siree.