A pair of quotes on the Presidency as noted by America's first president and by one of America's foremost legal scholars (a/k/a George Washington & Joseph Story)....
Washington: In our progress toward political happiness my station is new; and if I may use the expression, I walk on untrodden ground. There is scarcely any part of my conduct wch. may not hereafter be drawn into precedent. - letter to Catherine MacAulay — 1790
Story: On the other hand, the duty imposed upon him to take care, that the laws be faithfully executed, follows out the strong injunctions of his oath of office, that he will "preserve, protect, and defend the constitution." The great object of the executive department is to accomplish this purpose; and without it, be the form of government whatever it may, it will be utterly worthless for offence, or defence; for the redress of grievances, or the protection of rights; for the happiness, or good order, or safety of the people. - Commentaries on the Constitution, 1833
Washington makes a good point above; as America's first president, everything he did, from delivering addresses to Congress to leaving office after two terms (thus setting what is now codified into the Constitution as the 22nd Amendment) was untrodden ground, for having led America to its' independence from Great Britain, he now had to prove that Americans had made the right decision.
Story makes a good broad point above in that, as Chief Executive, the President is tasked with enforcing the laws on the books, that he carry out the duties of the office and that he represent America to the world as both head of state and as head of government, a marked contrast to most countries which separate the two divisions of power in separate offices.
