There will be blood tests. Interrogations about junior high. An analysis of tax returns.

It is an experience Joseph R. Biden Jr. knows all too well from his time on the vice-presidential short list 12 years ago.

Much about Mr. Biden’s own search for a running mate has been nontraditional. He has publicly mused about his criteria. He is not considering men. Above all, his choice could be the most important in years: At 77, Mr. Biden has said he views himself as a “transition candidate.” Left unsaid: His vice president could very well end up being the president next.

Yet as much as Mr. Biden’s process is unique, its contours are familiar. Late last month, he told a local television station that his campaign had begun “doing the background checks” — the latest sign that he is moving toward a short list of candidates.