An appeal to Latino voters? A dig at Mitt Romney for declining to release more of his tax returns?

How about both?

On Tuesday afternoon, Vice President Joe Biden made an address to the National Council of La Raza conference in which he trotted out a new double-barreled attack on the presumptive GOP nominee.

“Mitt Romney wants you to show your papers, but he won’t show us his,” Biden told the Las Vegas conference, according to his prepared remarks.

The provocative line’s debut comes as both campaigns are working to woo Latino voters.Last month Obama and Romney delivered back-to-back addresses at the NALEO conference of Latino officials, an event that came on the heels of Obama’s announcement that his administration will halt the deportations of some immigrants who were brought to the United States illegally as children.

Hector Barreto, former head of the Small Business Administration and co-chairman of Romney’s Latino outreach effort, responded by pointing out that Biden’s address “comes on the heels of yet another disappointing jobs report which showed that the second quarter of this year was the worst quarter of job creation in two years.”

“We have now had 41 straight months of unemployment above 8%,” Barreto said in a statement. “For our Hispanic community, the situation is even more precarious, with the unemployment rate stuck at 11% and for our youth between the ages of 16 and 19 at a staggering 31%. Regrettably, President Obama’s answer to our economic troubles is to set up the U.S. economy for one of the biggest tax increases in history in 2013. Increasing taxes on any American at this time is the wrong policy at the wrong time. Either the President does not recognize that or chooses to ignore it for political purposes.”

Biden’s remarks come as the Obama camp is renewing its calls for Romney to release more than a decade’s worth of tax returns. Romney earlier this year released his 2010 returns, but Democrats have hammered him for not releasing 12 years’ worth of returns, as his father, George Romney, did when pursuing his own presidential bid.

In a Radio Iowa interview taped Monday, Romney maintained that there’s “nothing hidden” in his tax returns.

And Colorado Attorney General John Suthers, a Romney surrogate, told reporters in Grand Junction, Colo., before the candidate’s town hall meeting Tuesday that he believes Romney has been sufficiently transparent about his finances.

“I think he needs to stay on message on the economy,” Suthers said. “That’s what people care about. These folks don’t care about Cayman Islands investments, they really don’t. They care about their own jobs, their own lives and they’re hurting, there’s no question about it.”

Asked later whether he would release more tax returns than Romney has, Suthers snapped: “Don’t ask me those kinds of questions. I’m not the candidate. Governor Romney will make the disclosures that he thinks are appropriate.”

Other Romney surrogates, meanwhile, have taken a different approach to the tax-return issue.

In an appearance on CNN’s “Starting Point” Tuesday morning, Rep. Jason Chaffetz (R-Utah) said of Romney’s decision not to release his tax returns that Democrats should “get over it.”

“[Romney’s] been very successful,” Chaffetz said. “He has released everything that is required to be released, including paying more than 16 percent of his income to charitable giving. So I think it’s a diversionary tactic. Most people don’t care about this. Governor Romney has been very successful. Get over it. It’s a reality. He’s been successful. That’s the kind of guy I want to be president. He actually knows how to turn the economy around.”

Excerpts of Biden’s La Raza remarks as prepared are below:

You’re the fastest-growing population. You now make up more than 16 percent of the population. But there are voices among us who fear your inclusion. This is not new. There have always been fights between the voices of inclusion and the voices of exclusion. Between those pushing us forward and those who keep pulling us back. Between those appealing to our hopes, and those appealing to our fears. ...

Imagine what the Supreme Court will look like after four years of Governor Romney. Imagine what it will act like. Imagine what it will mean for civil rights, voting rights, and so much we have fought so hard for. Imagine a Justice Department that supports, rather than challenges, continued efforts to suppress the right to vote. Because that’s what will happen if they win. ...

This is a man whose idea of tax reform is to maintain the Bush tax cut for the very wealthy, which costs $1 trillion, 55% of which goes to just 120,000 households in America, households of an average income of $8.4 million.

And on top of that, an additional $1.6 trillion tax cut to people with incomes in excess of a million dollars, which is a $250,000 per year tax cut for the average millionaire.

A budget that strikes 200,000 students from Head Start, 19 million poor off of Medicaid, as many as eight million cut from supplemental nutrition assistance. Child nutrition, school lunch program, child care, early education.

The impact on the Hispanic community would be devastating—and the effects would last a generation. And he says the President is out of touch? ...

When his father, George Romney, was a candidate was for President in 1968, he released 12 years of tax returns because, as he said, ‘One year could be a fluke, perhaps done for show.’ His son has released one year of his tax returns. Making a lie of the old adage: Like father, like son. Mitt Romney wants you to show your papers, but he won’t show us his. So many questions …

Philip Rucker and Amy Gardner contributed to this report.