WASHINGTON - The "legacy thing" may be harder than Barack Obama imagines.
Beginning his second term, Obama has a focused, though unstated, agenda: to achieve presidential greatness in the eyes of historians and Americans.
In this, he will almost certainly fail. He is already a historic president as the first African-American to be elected, but there is a chasm between being historic and being great.
Presidents are ultimately judged not by their total record, or by their ability to enact their agendas, or by their popularity.
They are judged by whether they get a few very big decisions right or wrong. Lyndon Johnson is mostly remembered for failure in Vietnam; it overshadows the passage of two landmark civil rights bills and approval of Medicare and Medicaid.
Richard Nixon is not celebrated for creating the Environmental Protection Agency, expanding food stamps or opening talks with China; Watergate dwarfs all.
These appraisals are made while a president is in office and, more definitively, after he's left.
Does a president's performance stand the test of time based on what happens later? Did his policies advance or retard the nation's well being? Were they wise or simply expedient?
Depending on the answers, much else can be forgiven or forgotten, as Robert Merry shows in his engaging book "Where They Stand: The American Presidents in the Eyes of Voters and Historians."
Consider Harry Truman.
For his last year in office, he was deeply unpopular. His approval rating hit a low of 22 percent. The Korean War frustrated Americans; the White House was accused of cronyism.
Yet, historians rank him in the top 10 presidents. Merry relates Truman's reaction to the Soviets' 1948 overland blockade of Berlin "to starve out the city [and] bring it under the Soviet yoke." His top advisers concluded that U.S. withdrawal was inevitable.
To which Truman responded: "We stay in Berlin. Period."
The Berlin Airlift followed.
"That decision helps explain why Truman is ranked so high by historians," writes Merry.
With hindsight, many momentous choices seemed correct: ending World War II with atomic bombs ("saving perhaps a million American lives," argues Merry); adopting the Marshall Plan and the policy of "containment" against the Soviets; desegregating the military.
Every school child knows the three "great" presidents: Washington, Lincoln and Franklin Roosevelt. They topped the first presidential ranking by historians in Life magazine in 1948. They've topped six subsequent rankings elsewhere.