Originally Published: 30 APR 23 11:10 ET

Updated: 30 APR 23 12:02 ET

By Jasmine Wright, CNN

(CNN) -- Vermont Sen. Bernie Sanders on Sunday brushed aside concerns about President Joe Biden's age following the president's reelection bid announcement, saying "Age is one thing. I think experience is another."

The independent senator, who, at 81, is a year older than Biden, told CNN's Dana Bash on "State of the Union" that "if you believe in democracy -- you want to see more people vote, not fewer people vote, I think the choice is pretty clear. And that choice is Biden."

Sanders, who caucuses with Democrats in the Senate, endorsed Biden's reelection bid last week, and the president is likely to enjoy an easy path to the 2024 Democratic nomination. Author Marianne Williamson and anti-vaccine activist Robert F. Kennedy Jr. are challenging him in the primary, but no major Democratic candidates are expected to join them.

But at 80, Biden is the nation's oldest president. Polls have consistently reflected concern about his age, even among Democrats.

Although there are clear moments when Biden is visibly slower physically than he was, dozens of aides, administration officials and members of Congress who've spent time with him have relayed stories to CNN about how thorough and demanding he is in meeting after meeting.

Sanders, who is up for reelection 2024 but has yet to detail his plans, said Sunday that the key for Democrats to hold the White House rests in a stronger focus on "working-class issues."

The party, he said, has "got to make it clear that we believe in a government that represents all, not just the few. Take on the greed of the insurance companies, the drug companies, Wall Street, all the big money interests, and start delivering for working-class people."

"You do that," he said, "I think Biden is going to win in a landslide."

Biden conceded earlier this month that he "took a hard look" at his own age as he contemplated whether to seek reelection.

"(The American electorate is) going to see a race, and they're going to judge whether or not I have it or don't have it. I respect them taking a hard look at it. I take a hard look at it as well -- I took a hard look at it before I decided to run, and I feel good, I feel excited about the prospects," Biden said when pressed on his age during a joint news conference alongside South Korean President Yoon Suk Yeol at the White House.

"With regard to age, I can't even say I guess how old I am. I can't even say the number -- it doesn't register with me," he joked.