For the past year, Mr. Wilson has devoted himself with the single-mindedness of a college-age groupie to following Mr. Romney around the country in decidedly conspicuous style: driving a pickup truck festooned with 27 giant Romney for President posters. (The largest are the size of a refrigerator.)

Forgoing home-cooked meals and forbearing horrendous traffic, he has driven, sometimes nonstop, from Omaha to Charlotte, N.C., (19 hours), Portsmouth, Va., to Tampa, Fla., (14 hours) and Des Moines to Manchester, N.H., (22 hours), showing up, almost without fail, just in time to greet guests outside of a Romney event…

He made the decision to spend 11 months of his life shadowing Mr. Romney on something of a whim. In July, he met the former Massachusetts governor at the Iowa State Fair, terrain that Mr. Wilson knew well from growing up on a hog and cattle farm in the state, where his father and godfather had been active in Republican politics. He had dabbled in campaigns himself, mostly in Virginia, as a volunteer…

Over time, he has become unexpectedly valuable to the campaign: a highly recognizable landmark for drivers trying to find an event; tangible evidence of Mr. Romney’s down-home appeal; and, perhaps most important, an accessible, garrulous and charming counterpoint to a sometimes awkward candidate. “You don’t know it yet,” Mr. Wilson once told a campaign worker, “but you need me.”