"As president, I will do everything I can to pass immigration reform and a path to citizenship," Sanders said at a televised Democratic town hall, held two days before Nevada's first-in-the-West nominating contest.
Pressed on how quickly he would move on the issue, the senator from Vermont replied, "I'm not a dictator here; it has to do with a little bit of cooperation from the Congress."
"It makes no sense, it breaks up families, it is burdensome," Clinton said to a round of applause. "We're going to end it."
The forum, sponsored by MSNBC and the Spanish-language network Telemundo, was devoted to issues of concern to the Latino community, with Sanders and the former secretary of State appearing back-to-back. After winning a coin toss, Sanders appeared first.
With audience questions in Spanish and English, the forum gave the candidates a platform to expand their appeal beyond the largely white electorates in the Iowa caucuses and New Hampshire primary.
Clinton, who in 2008 opposed driver's licenses for immigrants in the country illegally, explained her change of heart since her last run for president.
"Back then, it was a state-by-state determination, and I'm happy that most states have understood and moved in the right direction," she said.
The former first lady also went on the attack when asked about Sanders criticizing former President Bill Clinton for his record on Wall Street deregulation, the
Clinton said the average income rose for African American and Latino families more than it did for others as part of a broad economic rebound during her husband's presidency. She then faulted Sanders for calling
"Maybe it's that Sen. Sanders wasn't really a Democrat until he decided to run for president," she said. "He doesn't even know what the last two Democratic presidents did."
The audience booed loudly. Sanders spent most of his decades in politics as a political independent before seeking the Democratic Party's nomination, though he has always caucused with Democrats in Congress.
"It happens to be true," Clinton continued. "And I got to tell you, I look at our last two Democratic presidents — were they perfect? No. No person is. But I'll tell you what: I would take the two of them over any Republican — anytime, anywhere."
Immigration dominated the two-hour event. Asked to explain his vote against a 2007 immigration reform bill — something Clinton has criticized him for — Sanders cited a provision to allow guest workers into the country that he found unacceptable and "almost akin to slavery."
He pointed out that several major immigrant rights leaders also opposed the bill on those grounds. "I don't want to see workers in this country exploited," Sanders said, noting he backed a 2013 immigration bill that he considered much improved. That bipartisan measure passed the Senate but stalled in the House.
Sanders later denounced Republican presidential hopeful Donald Trump, saying he was scapegoating Latinos and Muslims.
The senator also said he was appalled at efforts by Republicans to delegitimize the president by suggesting he was born, like his father, in Kenya. Sanders mentioned his own father had immigrated from Poland.
"Gee, what's the difference?" he asked. "Maybe the color of our skin."
Both candidates were also asked about other matters, including Apple refusing the FBI's request to extricate data stored on a cellphone used by the attackers in the San Bernardino massacre.
"This is a very complicated issue," Sanders said, noting the need to balance security concerns with individual privacy rights.
"Frankly, I think there is a middle ground that can be reached," he said in a response echoed later by Clinton. Neither explained how they'd resolve the conflict.
Sanders was also asked about his criticism of Obama and former President Clinton. He said he believed that overall Obama has done "an outstanding job" but that he differs with him on some issues, including the administration's proposed Trans-Pacific Partnership, a trade pact with Asian nations. Sanders suggested the deal would hurt American workers.
He listed his main disagreements with Bill Clinton, but allowed that overall he'd done a "pretty good" job as president. Later, he revised that to "a good job."
It should be no surprise, Sanders added, that a senator would disagree with a president of his own party, noting how difficult it is to shepherd lawmakers on Capitol Hill. He then motioned to Senate Democratic leader Harry Reid of Nevada, who was seated in the Las Vegas audience and smiled in return.