WOLFEBORO, N.H. — Aides to Mitt Romney have pored over video footage of potential running mates, studying hundreds of hours of Sunday news show appearances, campaign debates and stump speeches for insight into how they handle unwelcome inquiries, even hecklers.

They have instructed possible No. 2’s to fill out a questionnaire with about 80 detailed and sometimes intrusive questions covering the financial and the personal, including, “Have you ever been unfaithful?”

And they have listened for political intangibles that are subjective but potent, like: is a candidate’s style of speaking inviting or grating?

The Romney campaign has cloaked its vetting of possible vice-presidential nominees in layers of secrecy, so much so that it is even considering using a decoy — two sets of planes, two rollout locations, for example — to try to keep the selection from leaking out.