There are times when it's important for Christians to be politically shrewd. In the US, that's been the case since the 70s (if not before then).
That said, it can be morally and spiritually hazardous to be too crafty and cunning. I'm reminded of C. S. Lewis's experience writing The Screwtape Letters. Now that's one of his most deservedly popular works. Psychologically penetrating.
Problem is, to write it, he had to assume the Devil's viewpoint. Had to think like the devil. He found it oppressive to cultivate that mindset. He could hardly wait to finish writing the book and put it behind him.
When it comes down to making calculations about whether it's more prudent to vote for Trump or Hillary (or Bernie), I feel like I'm crossing a border into Screwtape territory. If it comes to that, the remaining options will be so appalling that I'm having to apply an almost devilish ingenuity to their comparative merits. I don't want to spend much time on that side of the border. I don't want to become acclimated to that side of the border.
Admittedly, that's a melodramatic comparison. But there's a grain of truth to it. There's a point at which I find the calculations morally self-degrading.