When John Winthrop delivered a sermon to his Puritan band before the Arbella made landfall in 1630, he set flying a beloved political cliché - one now elevating the resurgent campaign of Newt Gingrich. “For we must consider that we shall be as a city on a hill,’’ Winthrop declared. “The eyes of all people are upon us.’’ Recently, Gingrich screened his documentary, “A City Upon A Hill: The Spirit of American Exceptionalism,’’ at Harvard’s Kennedy School. This was an apt setting, since it was John Kennedy, speaking on the eve of his inauguration, who stamped the contemporary political lexicon with the image, a reference both to a saying of Jesus and mystic Jerusalem. But it was Ronald Reagan who made the phrase so dear to the conservative heart. He began and ended his presidency by invoking the “shining city,’’ always with a lump in his throat.