As the famously voluble Mr. Biden makes his first retail campaign stops in the Democratic primary, and grows accustomed to the front-runner status he never enjoyed in his two previous White House bids, his campaign is grappling with how to showcase Mr. Biden’s never-met-a-stranger persona without exposing him to an environment where he may commit a gaffe.

So far, they have struck a safe, if precarious, balance.

Just over two weeks into Mr. Biden’s candidacy, the most notable feature of his campaign may be what hasn’t happened: He has not blurted anything out that delights his rivals, horrifies his aides and reinforces his image as “Uncle Joe,” America’s there-he-goes-again relative who makes you smile and wince in equal measure.

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It is early yet — which even Mr. Biden’s friends allow as they hold their breath — and precedent offers good reason to question whether his streak of mostly error-free days can last.

But his staff has sought to mitigate the risk by effectively recreating the trappings of the vice presidency: guarding question-and-answer sessions, selecting safe interview settings and remaining all but glued to his hip when he greets voters on rope lines, dips into ice cream shops and steps out of the black Chevy Suburbans that are indistinguishable from the Secret Service models he once rode in.

There are notes on his lectern to remind him of key policy points, depending on the locale, and his schedule has been carefully planned: He has appeared at nearly as many fund-raisers (five) as he has rallies (six).