Sen. Bernie Sanders, I-Vt., said Thursday that he does not see "many alternatives" to supporting President Biden for re-election in 2024, having decided against running for president himself. 

"I don't think one has many alternatives," Sanders told MSNBC host Chris Hayes. "What's at stake is the future of American Democracy." 

"What's at stake is whether we have some right-wing demagogue running this country or pathological liar, somebody who's trying to divide us up," he continued. "Or whether we re-elect somebody who is a very decent human being who's trying to do the opposite, trying to bring the American people together." 

On Tuesday, Sanders endorsed Biden for re-election and discouraged other high-profile progressive candidates from challenging the president in the Democratic primary. 

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Senate Health, Education, Labor and Pensions Committee Chairman Bernie Sanders (I-VT)

Sen. Bernie Sanders, I-Vt., is not running for president in 2024 and has endorsed President Biden for re-election. (Chip Somodevilla/Getty Images)

Biden on Tuesday made official his decision to seek a second term, even as polls suggest that voters in both parties do not want him to run again. The Democratic president is expected to defeat his long-shot primary challengers and face the winner of the crowded Republican primary, which features former President Trump and a half dozen lower-profile conservatives.

Sanders is a firebrand progressive who gained a large following in the Democratic Party with his unsuccessful 2016 and 2020 presidential campaigns. Though he is critical of Biden on several policies, the independent said progressives should rally around the president to keep a Republican out of the White House. 

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Sen. Bernie Sanders and President Joe Biden

Sen. Bernie Sanders, right, was Joe Biden's chief rival in the 2020 Democratic primary, winning the popular vote in the Iowa caucuses and New Hampshire Democratic primary. (MANDEL NGAN/AFP via Getty Images)

"I think it is a surprise to nobody when I say I disagree with Biden on many issues," Sanders said Thursday elaborating on his decision. "But on the other hand I think he deserves credit for what he has accomplished. And our job now as a progressive movement is to rally the people of this country to make sure that the next four years complete some of the efforts that have begun in the first administration."

Biden's approval rating hit an all-time low this week as he seeks re-election. 

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Williamson, Biden, Kennedy

From left to right, 2024 Democratic contenders Marianne Williamson, President Biden and Robert F. Kennedy Jr. (Scott Olson/Ting Shen/Joseph Prezioso)

A Gallup survey found that just 37% of U.S. adults approved of Biden's job performance as president, the lowest since July 2022 when just 38% said they approved. A whopping 59% of adults said they disapproved.

According to Gallup, Biden's approval rating has hovered in the low 40s for the last 19 months, down from a high of 57% immediately after he took office in January 2021. The most recent poll drops his average (39.7%) over the ninth quarter period of his presidency to below that of former President Trump (41.6%) during the same time period.

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Even so, with Sanders and other high-profile Democrats so far declining to enter the race, Biden only faces token opposition for the Democratic nomination from Robert F. Kennedy Jr., an environmental lawyer and anti-vaccine activist, and self-help author Marianne Williamson. 

Fox News' Brandon Gillespie contributed to this report.