Even the men who are in contention to become Mitt Romney’s running mate are in the dark about what is going on. One of the finalists has said privately, “Each of us assumes it’s going to be somebody else.”

But when will they know? And when will the rest of us know?  There’s a school of thought in the extended Romney camp that the identity of the pick will dictate the timing of the announcement.  A choice that is more exciting to the Republican base, and to the GOP convention delegates, can be announced late, even at the convention itself, because it will instantly excite Republican loyalists.  No need for an extended sales campaign.  But a pick that is less exciting to the base might be announced earlier, to give Romney time to build support for his choice.

“If he picks Rubio, he could do that the day before the convention, and it would electrify the convention and be exciting,” says one source who is familiar with the campaign but not part of the vice presidential process. “[The delegates] want Rubio, or maybe Christie, or perhaps Paul Ryan.  But if he chooses Portman or Pawlenty, he should do it enough in advance so that he doesn’t immediately go in and disappoint the convention.  It gives him time to sell his choice.”

This person, as well as others who know Romney, believes Romney’s innate caution will guide his choice, meaning that Portman, or perhaps Pawlenty, remains the most likely pick.  For a number of reasons that I wrote about yesterday — including Romney’s belief that his campaign is on the right track and does not need a jolt to succeed — a number of semi-insiders continue to believe that Portman and Pawlenty top the list.  But they, like the contenders themselves, don’t really know.