Authors: When presidents turn to ex-presidents for advice

(CBS News) Two books on the presidency depict different aspects of the challenging job of making the right decisions of the time and the impact those decisions will have on a president's legacy.

On "Face the Nation," Time Magazine editors Nancy Gibbs and Michael Duffy discuss their new book titled "The President's Club," which looks at the relationships between current and past presidents.

Gibbs said she was "surprised" by how often former and current presidents communicate. "We see this going back to Harry Truman reaching out to Herbert Hoover, who was a pariah still, and secretly mailing him a letter asking him to come into the White House and help him out," Gibbs said.

Hoover started the "modern president's club," Gibbs said. "There is Truman who suddenly finds himself in office in the spring of 1945 and he's facing this catastrophe in Europe as the war is ending and he secretly writes to Hoover saying can you come help me figure out how we're going to get food to the countries that need it? These two, they're very suspicious of each other. Again they have nothing in common, and yet they end up forming this partnership that you could say probably saved more lives than any two men in the twentieth century, and worked very closely together throughout Truman's presidency."

Duffy added that there is "almost automatic sympathy" between the current president and his predecessors. "They all study each other. They have their own rating system. They compare themselves to each other. They read each other's biographies and memoirs carefully. They're looking for lessons. They're looking for sympathy. They're looking for understanding."

He explained with the anecdote: "Nancy [Gibbs] once asked George W. Bush, not too long after he'd been in office, 'Do you think differently about Bill Clinton now?' And he said, 'Oh, I think differently about all of them.'"

Also joining the discussion was Robert Merry, the author of the upcoming book, "Where They Stand: The American Presidents in the Eyes of Voters and Historians," which examines presidents' success rates.

Merry said six presidents meet his test of greatness: George Washington, Thomas Jefferson, Andrew Jackson, Abraham Lincoln, Theodore Roosevelt and Franklin D. Roosevelt.

Merry ranks presidents based on three tests: Voters' perspective, if the two-term president's party wins after he leaves office, and if they "changed the political landscape and redirected the country."

Merry also suggested adding Ronald Reagan to the list, with an asterisk: "Reagan met the voters' test, he met my test of redirecting the country, but he hasn't yet risen up to those upper levels consistently in the historian polls."

Schieffer asked if people can determine mid-presidency if a president is going to be successful. Merry said no: "You really can't. You can't say even, even some years afterwards. There has to be a given time for history to make a judgment."