NEW YORK (AP) - Even in the earliest days of the new year, a harsh reality has settled over U.S. politics: The 2020 presidential contest promises to be the fiercest political battle in living memory. Bitter divisions are already threatening to weaken both political parties from within. President Donald Trump has begun to hurl personal and policy attacks at his potential Democratic opponents, even inviting assistance from foreign governments. And a great political realignment is disturbing decades-long political alliances that will further divide America by education, gender and race. Welcome to 2020, an election year that will serve as a referendum not only on the candidates, but also the country and its definition of the American presidency.