While largely unspoken, both sides acknowledge that Republicans would be best served by not reminding voters of the Bush legacy of gaping budget deficits, two wars and record low approval ratings. His eight-year presidency has merited no more than a fleeting reference from Romney and his rivals in debates, campaign stops and interviews.

"For now we're just staying out of it," George W. Bush spokesman Freddy Ford said Thursday, declining to comment on a possible endorsement. Ford said Bush was focused on promoting and developing a presidential library bearing his name at Southern Methodist University.

"That's really where he's spending his time," Ford said.

But George W. Bush's virtual invisibility from the presidential contest seemed to surprise even his 87-year-old father Thursday, as a handful of reporters visited the senior Bush's private office in Houston to watch him endorse Romney.

"Has he endorsed you?" George H.W. Bush quietly asked Romney as reporters were beginning to the leave the room.

"Uh, no, no," Romney responded, before Barbara Bush quickly ended the conversation: "We'll talk about that," the former first lady said.