PHILADELPHIA — Although President Obama has nearly three years left in his second term, plans for his presidential library are starting to take shape. On Jan. 31 came the announcement that the Barack H. Obama Foundation had been formed to “manage the library planning process.”

Chicago, where Mr. Obama made his home and built his political career, seems the likeliest site, but people in Honolulu, where he was born, and New York, where he finished college (at Columbia) and where he is believed to want to live after he leaves the White House, are making the case for their cities.

There is speculation in the architectural press that the British architect David Adjaye, who is designing the National Museum of African-American History and Culture on the Mall in Washington, has the inside track for the commission.

But where the library is situated or who designs it is less important than whether Mr. Obama will follow the grandiose example of his predecessors, or chart a new course....