"Every once in a while I wanted to say: 'Joe, tell the rest of the story.'"

Jimmy Roosevelt had just heard Joseph Alsop, political columnist emeritus and a distant relative, talking about his father and "The Roosevelt Enigmas" in a lecture marking the centennial year of the birth of Franklin Delano Roosevelt.

The Alsop talk brought together some who remembered the Roosevelt years and others who could only imagine that era but felt the impact on their lives nearly a half-century after his death.

There was no enigma about how Alsop felt about Roosevelt's presidency: "It is the good fortune of the United States that Franklin Roosevelt was one of the good great men, and thus far indeed, we Americans have always found good great men to lead us in all our rare times of genuine peril."

Alsop, speaking for an hour before an audience of nearly 300 guests in the Great Hall of the National Portrait Galley, spoke of three types of Rooseveltian enigmas, including those with clues or possible persuasive solutions. Then, he added that there is the puzzle with no thread to guide historians through the labyrinth of uncertainty.

Alsop, despite Jimmy Roosevelt's chiding observation, did tell the rest of the story with anecdotes. As an example of the enigma without clue or solution, he told the tale of how Roosevelt purposely "lost" himself in the Georgia countryside and finally forced desperate Democratic Party leaders in New York to call him at a remote rural telephone booth.

This was in 1928 when Al Smith had rounded up enough votes to ensure the Democratic Party presidential nomination but needed Roosevelt as the most likely Democrat to win the governorship of New York State. Earlier Roosevelt had demurred at making the race for governor. It wasn't an unequivocal "no," Alsop pointed out, but FDR had said he couldn't run because he had a good chance to walk again after polio if he went on with his interminable exercises in the pool at Warm Springs.

So Roosevelt played hard to get for the governorship -- a post he had wanted for years -- and made the politicians feel that he was doing them a great favor.

For Alsop, the enigma remains: Did Roosevelt really believe that prolonged exercise might permit him to walk again? Or did he half-believe it? Or just pretend to believe it, although "there can be no doubt that Roosevelt coolly exploited his withered legs to force Smith and other New York leaders to beg him to run for the governorship."

Alsop, in black-tie for a proper lecture, spoke with both feeling and perception for FDR and his era. The political journalist, who covered the New Deal from 1935, spiced his discussions with some sly observations on present times and politicians.

"Imagine Roosevelt nervously consulting private pollsters to learn where the majority wanted him to go at the moment," Alsop asked the audience. "Imagine him hiring a professional image-maker to titivate what is now so horribly called his image."

It was Roosevelt's extraordinary sense of timing -- without poll-takers to advise him -- that allowed him to prepare the country for World War II, moving as rapidly as he could muster support, Alsop emphasized. As for the enigma of Roosevelt's timing, Alsop said a clue lies in FDR's wide political experience and knowledge of Americans.

After the Alsop lecture last night, the guests attended a reception and wandered through a one-room exhibit of "FDR: The Early Years."

There were FDR's two sons, Jimmy and Elliott. And there were several of the Roosevelt grandchildren.

One of the items on exhibit is a Harvard transcript recording a C-plus grade in government for FDR. But it is likely the people at the lecture-reception last night would have upgraded that mark to A+.