CHICAGO  From a dismal parking lot on this city’s South Side, a bus is scheduled to pull out on Monday headed east, packed with people from the neighborhoods where President-elect Barack Obama first cut his teeth as an organizer hoping to make a difference in the world.

The riders on the Fellowship Bus, as they are calling it, are making a bare-bones 1,200-mile round trip to Washington to be present as Mr. Obama takes the oath of office. They are leaving without hotel reservations, an agenda of any kind or even much of a chance that they will get close enough to the Capitol to see the main event. Nor will they get much sleep, as the bus will turn around as soon as the inauguration is over.

But none of that matters much.

“We just had to be there for him,” said the Rev. David Bigsby, a Baptist preacher who has a seat on the bus. “He was such a blessing to our community and churches.”

The Rev. Len Dubi, a Roman Catholic priest who will also be on board, is already reminiscing about how he watched over Mr. Obama as a young community organizer trainee in the mid-1980s.