Romney himself has acknowledged making such missteps and he has vowed to improve.
Lately, he's started venturing to the back of his campaign plane to chat with reporters about the more mundane parts of life, like a dinner he planned to have with one of his five sons, whether he gets nervous on election days and whether he has a lucky tie.
Such exchanges project a relaxed, confident person - an image his campaign hopes will come through more in a general election than it has in the primary.
Still, it's clear his Boston campaign advisers don't want to push him too far. Romney took a call from them as his SUV navigated the L.A. freeways on his way to tape Leno's show.
"They said, 'Don't try and be funny, just answer the questions straight,'" Romney said in a video one of his aides posted on Twitter. "I'm rarely funny on purpose, so we'll see what happens tonight."
Associated Press writer Brian Bakst contributed to this report.
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