Down-home and laid-back, Joe Biden has been traveling the country saying what few politicians could about their opponents, for better or worse.

Mitt Romney is “etch-a-sketchy,” the vice president said this week.

Last month, he told a Hispanic audience: “Romney wants you to show your papers, but he won’t show us his.’’

At a campaign rally Thursday in Las Vegas, he said Paul Ryan and other young Republican leaders in Congress, nicknamed “young guns,” have “their bullets aimed at you.”

Biden has a long history of edgy verbal blurts — in 2007, he described then-Sen. Barack Obama as “articulate” and “clean,” a comment he later said he regretted. But in the week since his blustery debate with GOP vice-presidential nominee Ryan, Biden seems to have found a slightly different niche — a more deliberate delivery of his sometimes-outrageous utterances. He offers these with a smile, relishing the stage, often punctuated by a “Whoa!”

“When Governor Romney was asked a direct question about equal pay, he started talking about binders. Whoa!” Biden said on a campaign swing this week. “The idea that he had to go and ask where a qualified woman was, he just should have come to my house. He didn’t need a binder.”

Within the Obama campaign, there is a cautious fear that Biden will go too far. Transcripts of his remarks are not regularly distributed, unlike President Obama’s and the first lady’s. And the vice president’s aides have sometimes tried to steer him away from unscripted encounters with reporters.

But Biden also fills a strategic role for the campaign. With evidence that his middle-class Joe ethos has made him a beloved figure among rank-and-file Democrats, the campaign has regularly dispatched him to working-class communities, union-heavy gatherings and events aimed at Latino voters.

He has been a regular presence in Ohio, perhaps the most critical state on the electoral map. He also has traveled often to Florida and Iowa and just returned from a campaign event with union members in Las Vegas. Overall, Biden has racked up appearances at more than 100 campaign events this year.

Campaign officials have decided to let Joe be Joe. “He has an ability to connect and communicate in a clear and effective way,” Obama campaign manager Jim Messina said in recent interview. “He, like the president, embodies an American success story.”

Republicans say Biden has repeatedly crossed the line of decorum, and political analysts wonder whether he’s gone so far as to become unpresidential.

“Today’s over-the-top rhetoric by Vice President Biden is disappointing, but not all that surprising,’’ Ryan spokesman Brendan Buck said after Biden’s “bullets” remark this week. “In the absence of a vision or plan to move the country forward, the vice president is left only with ugly political attacks beneath the dignity of the office he occupies.’’

William A. Galston, an aide to President Bill Clinton who is now a senior fellow at the Brookings Institution, said he’s “never seen a less presidential demeanor from a national candidate.” Biden has twice run for president and has not ruled out a third attempt in 2016.

“His role is the classic vice president’s role: to attack relentlessly and to be full-throated in defense of the administration,” Galston said. “It’s straight out of the VP 101 class.”

Biden and his supporters say he is just being honest.

“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,” Biden’s son Delaware Attorney General Beau Biden (D) said in a recent interview.

Polls show both sides of the coin. More than three in four Democrats view Biden favorably, but among all registered voters, the vice president is much less popular than he was as a running mate in 2008. In a Pew Research Center for the People and the Press survey early this month, Biden was viewed favorably by 39 percent of voters and unfavorably by 51 percent. In fall 2008, more than half of voters had favorable views of him.

A survey by The Washington Post and the Pew Research Center at the end of the summer found disparate views of the vice president. Single-word descriptions of him included “good,” “honest,” “clown,” “buffoon” and “idiot.”

Biden interjects more light-hearted moments into his campaign rallies than Obama, Romney or Ryan. While he generally sticks to his themes, he is prone to ignore the teleprompter, ad-libbing as he looks directly at the crowd.

His audiences often talk back to him, energizing Biden and sending him on riffs. When he made his “young guns” comment, for example, he was responding to someone in the crowd who had shouted out, “They have guns with no bullets!”

Of his opponents, he has repeatedly said, “These guys are out of touch” while laying out the campaigns’ differences on immigration, abortion rights and economic policy.

At the Republican National Convention in August, “they discovered the middle class!” Biden said to laughs. “It’s like: ‘My God, there it is! It’s out there! There is a middle class! We are concerned about it! We share your values! Whoa! God, I didn’t see you there, I don’t know how I could’ve overlooked you these last eight years. You’re right in front of me.’ It was amazing.”

While speaking to voters, Biden often tells the story of his father losing his job and the devastating impact that had on the family. When others tell Biden’s story of becoming a widower soon after being elected to the Senate at age 29, it often prompts a visible wave of emotion across the audience.

Describing what he says are Romney’s changing and disappearing policy positions, Biden repeats a question from his granddaughter: “Was it Casper the Ghost who did this, Pop?”

Biden will campaign again in Ohio next week, and voters there know what to expect.

“Joe Biden is Joe Biden, and he was elected to the Senate before the age of 30 and has been absolutely the same from the beginning of his political career to the end, if this election is the end,” Galston said.

Scott Clement contributed to this report.