The Supreme Court itself is a partisan institution, now more than ever, and every reading of the Constitution has been subject to partisan biases since forever. That's not to say we have no checks and balances, just that they are not independent. More like interdependent and part of a vicious cycle; biased legislators appoint biased judges who exonerate biased executives who reward biased legislators. I think the cycles of the last few years have made that abundantly clear, but any cursory reading of US history should reveal this is not a new pattern. It's just how the system has always worked, our folklore notwithstanding.