Romney has said his choice will be announced sometime in the next three weeks, and the campaign earlier this week released a new smartphone app that promised users would be alerted first when a decision was made.

But otherwise the campaign has been tight-lipped about its deliberation process, even with a decision expected any day. On Wednesday, The Wall Street Journal reported that the campaign was bulking up its vice presidential staff, and top candidates for the spot spent the past week stumping on Romney's behalf while the candidate was overseas.