“But let me take this moment, if I might, to thank so many people from all over this country, including many of my colleagues up here, for their love, for their prayers, for their well-wishes,” he continued. “And I just want to thank you from the bottom of my heart, and I'm so happy to be back here with you this evening.”

Tuesday’s forum was the first primary debate since Sanders’ campaign announced earlier this month that had two stents inserted to address a blockage in an artery, and his doctors revealed days later that he had suffered a heart attack.

Sanders took a brief hiatus from the campaign trail following his hospitalization, which renewed concerns about the 78-year-old candidate’s physical fitness to assume the presidency.

But the progressive lawmaker remained light-hearted about the episode Tuesday, fielding the line of inquiry on his health after his primary rivals were queried on drug decriminalization and the prosecution of pharmaceutical executives.

“I'm healthy. I'm feeling great, but I would like to respond to that question,” Sanders interjected.

Amid a smattering of applause and laughter, New Jersey Sen. Cory Booker chimed in: “Sen. Sanders is in favor of medical marijuana, I want to make sure that's clear, as well.”

“I'm not on it tonight,” Sanders quipped back.

Former Vice President Joe Biden and Massachusetts Sen. Elizabeth Warren, the two septuagenarian frontrunners in the party’s nominating contest, were also asked questions related to their ages.

Biden, 76, said he was sure he could undertake the duties that accompany the Oval Office “because I’ve watched it. I know what the job is. I've been engaged.”

“Look, one of the reasons I'm running is because of my age and my experience. With it comes wisdom,” he said, adding: “I know what has to be done. I will not need any on-the-job training the day I take office.”

Asked to respond to a survey showing that 40 percent of Democratic primary voters say a candidate under the age of 70 is more likely to defeat Trump, Warren — who would be 71 at the time of her inauguration — pledged to “outwork, out-organize and outlast anyone, and that includes Donald Trump, Mike Pence or whoever the Republicans get stuck with.”