President Biden will lock arms with two of his Democratic predecessors at a campaign fund-raising event on Thursday evening in New York City, a public display of support from the two men who understand like few others what he faces.

Yet in one key way he will be standing alone.

Of the triumvirate of recent Democrats in the White House, Mr. Biden is the one who historians, political strategists and policy experts argue has racked up the most expansive list of legislative accomplishments — and has received the least amount of credit for them.

In a first term with a closely divided Congress, Mr. Biden signed legislation to provide $1.9 trillion in pandemic stimulus, $1 trillion in infrastructure spending and $370 billion to fight climate change, as well as the first gun control measures in 28 years. It is a roster of achievement that surpasses Bill Clinton and Barack Obama, the two Democratic former presidents who will join him on Thursday in New York. And yet Mr. Biden’s approval ratings are the lowest of all three men. While voters broadly support some of Mr. Biden’s key policies, they are far more pessimistic about the future. And they’re not confident in his ability to serve a second term.

“His biggest problem is not so much his ability to get things done, as we’ve seen, but his ability to put together a message that reaches the average American, no matter where they’re located, whether it’s a red state or a blue state, and to be able to get them to understand just exactly what he’s trying to do for the country,” Leon Panetta, who served as Mr. Clinton’s chief of staff and also in Mr. Obama’s cabinet, said of Mr. Biden.

That central political paradox reflects the unique circumstances of the Biden era.

Mr. Biden is running in a tumultuous political climate unlike any the country has experienced before in modern times, seeking re-election in the first presidential contest since the pandemic was a major threat, the Jan. 6 attack on the Capitol and the Supreme Court’s ruling overturning a half-century-old constitutional right to an abortion.

Mr. Biden’s predicament also highlights just how deeply Americans have lost faith in politics and government since Mr. Clinton and Mr. Obama were in office.