"He's wrestling with the decision," the former president said on CBS' "Face the Nation." "I think it's 50-50. I'd give it a tossup."
Bush, the 43rd president, was promoting his new book about his father, former President George H.W. Bush, the 41st president, when he broached the prospect of a Bush as the 45th president, which has gained traction as the former Florida governor has increasingly signaled he may be interested in the job.
"I hope he runs," Bush said during the talk at his presidential library and museum in Dallas. He said he would campaign for his brother -- or stay behind the scenes, if that is preferred. "I would be one of his strongest backers," Bush said.
Another possible 2016 candidate, Republican Scott Walker, who won reelection last week as governor of Wisconsin, did not rule out his own bid Sunday.
Walker said that even though he's a fan of fellow Wisconsin Republican Paul Ryan, the fiscally conservative congressman often considered White House material, he believes his own message may be better against likely Democratic contender Hillary Clinton.
"I've said many times before: I'll be the president of the Paul Ryan fan club, but I do think if we're going to beat Hillary Clinton in this next election, we've going to have a message that says Hillary Clinton is all about Washington," Walker said.