Ann Romney, for her part, generally sticks to a script while campaigning for her husband, sharing warm and humorous stories about Romney family life and the challenges of raising five boys.
David Ropeik, a Harvard professor and author of several books on risk, said it's no surprise that the candidates are being cautious "in a no-holds-barred, 24-7, scream-a-thon world, where any hint of what the other side might see as an error is guaranteed to explode."
But Ropeik said both men need to know that being too careful can do them more harm than good.
"Candidates take a huge risk by being so buttoned up that they fail to express human sincerity," Ropeik said. "It's risky not to be sincere — even though sincerity is risky."
As the campaign progresses, the candidates may well adopt more risky strategies to further their own ambitions, especially if the race remains close.
Obama, for example, raised eyebrows this week with a tough new ad that goes after Romney's record at the Bain Capital private equity firm. The ad quotes a former steelworker who compared the firm to a "vampire" that sucked the lifeblood out of companies.
The populist pitch may help fire up Obama's base of support but risks making it more difficult for him to attract voters in the political center.
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