NORLFOLK, Va. —
Earlier in the day, Romney's campaign briefed reporters on the bus tour, making no mention of the impending vice presidential announcement.
"The governor keeps very close counsel on that, and I have no guidance," adviser Eric Fehrnstrom said of any potential event.
Romney's bus tour was expected to include appearances with Portman, as well as two others who had been talked about as possible contenders for running mate: Virginia Gov. Bob McDonnell and Florida Sen. Marco Rubio.
The tour will take Romney through four must-win states in as many days: North Carolina, Virginia, Florida and Ohio. All are battlegrounds where Obama won in 2008. While Obama could afford to lose in one or more of them and still reach the 270 electoral votes needed for another term, Romney almost certainly needs all four to beat him.
Peoples reported from Washington. Todd Richmond in Janesville, Wis., contributed to this report.