Ryan Lizza summarizes his very intelligent historical corrective to the prevailing (but fading?) illusion of the presidency's transcendent powers in this passage:
The boring fact of our system is that congressional math is the best predictor of a President’s success. This idea is not nearly as sexy as the notion that great Presidents are great because they twist arms in backrooms and inspire the American people to rise up and force Congress to bend to their will. But even the Presidents who are remembered for their relentless congressional lobbying and socializing were more often than not successful for more mundane reasons--like arithmetic.
The president's constitutional powers remain constant, while favorable presidential arithmetic comes and goes. Obama's first two years of success versus his subsequent, flatlining four (in play) prove the rule, as did President Johnson's tenure:
[His] celebrated legislative achievements were in reality only a function of the congressional election results--not his powers of persuasion. In 1965 and 1966, after the enormous Democratic gains of the 1964 election, Johnson was a towering figure who passed sweeping legislation. In 1967 and 1968, after he lost forty-eight Democrats in the House, he was a midget.
I would add as a matter of related interest the rather titanic shifts in our own predilections. Voters tend to be virtual monarchists when a president of their choice is in power, yet rapidly swing to Whiggism when the enemy occupies the White House. Under Bush II, for instance, most Democrats came to see their party's political function as one of restraining the president's ugly imperial authority, and yet they've fallen largely silent on the menace of a singular foreign policy and domestic executive orders since 2009; conversely Bush II's supporters, who adored W.'s high-handed and damn near despotic determination, instantly concluded one cold January afternoon that the only good president (well, you know what I mean, not really good) is a congressionally straitjacketed president.
And voters manage all this while never missing a beat; that is, they never acknowledge--especially to themselves--that just yesterday they were lovers of the throne, though today they're devout parliamentarians, or vice versa.
We're an odd little species.