Felicia Sonmez / The Washington Post

Vice President Biden’s off-script remark at a campaign rally Tuesday that the middle class has “been buried for the last four years” has rekindled debate over his effectiveness on the stump, with defenders contending that such gaffes are a sign of Biden’s authenticity, while critics argue that he has served as more of a punch line than an effective messenger on the trail.

With the vice presidential debate less than a week away, Republicans have begun ramping up their criticism of the No. 2 Democrat, noting that whereas Biden as a senator was a regular on the Sunday talk-show circuit, Biden the vice president has not sat for a national TV interview since the “Meet the Press” appearance in which he — apparently unintentionally — pre-empted President Obama in expressing support for same-sex marriage.

That appearance came five months ago — a point not lost on some of Biden’s detractors, some of whom contend that in addition to being gaffe-prone, the vice president sits down for interviews so infrequently he must be part of “an Obama-campaign-designed Witness Protection Program.”

“Thank you, Vice President Biden — for the first time in a long, long time, you’re right,” former New Hampshire governor and top Romney surrogate John Sununu quipped of Biden’s remark on a conference call with reporters Tuesday afternoon.

The vice president’s defenders see things differently. They contend that the occasional slip of the tongue is to be expected from a candidate as candid and unscripted as Biden. They point to the vice president’s busy schedule on the trail — he has held more than 100 campaign events this year alone, many in a host of battleground states — as proof that he is an asset to the Democratic ticket.

And they argue that Biden is spending his time doing what matters most — speaking directly to voters, particularly those in the middle class — at rallies as well as at his frequent stops at diners, school sports practices and local food stands.

At those informal events, they contend, Biden is accessible to the public and members of the news media alike, giving the vice president greater exposure than in TV interviews alone.

“They usually don’t go after you unless you’re landing punches, and this is about attempting to go after him in a way because he’s such an effective communicator for the middle class,” said Biden’s son, Delaware Attorney General Beau Biden.

“What matters here is two basic things: One is an understanding of the middle class, which my father knows and has lived and which Gov. Romney never will understand,” he added. “And Romney’s underlying policies will hurt the middle class, because they’re the same policies that got us into the mess that the president inherited. Everyone in that venue knew.”

The vice president’s “buried” comment, made at a rally in Charlotte, N.C., triggered an immediate onslaught of criticism from Republicans up and down the ballot.

Republican presidential nominee Mitt Romney tweeted that “the middle class has been buried the last 4 years, which is why we need a change in November.” His running mate, Rep. Paul Ryan, opened his remarks at a rally in Burlington, Iowa, by telling the crowd: “We need to stop digging by electing Mitt Romney as the next president of the United States.”