Joe Biden is betting on optimism, and so far he has much of the country on board.

To keep it going long enough to defy historical trends and avoid Democratic losses in the midterms, he’s counting on a surging economy and a swift rebound from the coronavirus pandemic.

And he wants to make sure voters are paying attention.

“After just 100 days, I can report to the nation, America is on the move again,” he said in his address to a joint session of Congress last week. “Turning peril into possibility, crisis into opportunity, setbacks to strength.”

A new ABC News/Ipsos poll released on Sunday found that 64 percent of Americans said they were optimistic about the direction the country would go in over the next year, including close to four in 10 Republicans. The new survey suggests Mr. Biden hasn’t lost ground since his inauguration, when a Monmouth University poll found just over three in five Americans were optimistic about the policies he would pursue as president.

In a moment when partisan gridlock has held Mr. Biden’s approval rating down, particularly among Republicans, optimism conveys a different — but perhaps equally meaningful — measure of the political climate.

“People are expecting optimism going forward, and it looks to me like it’s going to be extended beyond a few months,” Doug Sosnik, a political strategist and former senior adviser to President Bill Clinton, said in an interview, mentioning estimates of high G.D.P. growth in the coming year. “In the case of Biden narrowly, this is all positive for now.”

Optimism generally works in favor of the incumbent party, so a humming economy and feelings of positivity in 2022 would be the Democrats’ best bet for pulling off the improbable feat of retaining control of both houses of Congress.

But midterms are driven by turnout, and Mr. Sosnik said it was impossible to say whether, in such polarized times, optimism would materialize as votes.

“The trick is going to be that people have to feel so strongly positively about how their lives have improved that they will actually go out and vote in the midterms,” Mr. Sosnik said. “It’s less of an issue in a general election,” when turnout typically runs higher.

And with the advantage of high optimism, of course, come the perils that have confronted past presidents. When Mr. Clinton took office in January 1993, 61 percent said in an NBC News/Wall Street Journal poll that they were optimistic about the coming four years. Within a few months, his approval rating was negative. President George W. Bush saw a similar decline, until the attacks of Sept. 11, 2001, sent his approval soaring.

Around President Barack Obama’s 100-day mark in April 2009, 72 percent of Americans said in a New York Times/CBS News poll that they were optimistic about the coming four years of his presidency. But Republican attacks and legislative gridlock bogged him down, and his approval rating was soon stuck bouncing between the 40s and low 50s.

His party suffered enormous losses in the midterms, as the economic stimulus package he passed in 2009 failed to impress most voters and he emerged from an excruciating health care debate with a bill that received only mild enthusiasm from Democratic voters.

Today, with a considerably more divided public than just 12 years ago, Mr. Biden has started off with a different approach. He has been boldly partisan, signing numerous executive orders and passing and proposing trillions of dollars in legislation.

And he has been bold — though extra-careful — about promoting the work he has done. His administration quickly developed a reputation for its tight-lipped dealings with the press, but the president has not been shy about championing his vision for the country.

On Monday, he promoted his American Families Plan proposal in a speech at Tidewater Community College. “We can choose to give hard-working families a break,” he said. “We can choose to invest in our students. We can choose an economy that rewards work and not just wealth.”

Mr. Biden has even taken up a self-promotion tactic around the just-passed stimulus bill that calls to mind President Donald Trump’s approach. Last year, Mr. Trump had his name printed on stimulus checks sent out as part of a Covid-19 relief package, even though it was a Treasury official’s signature that authorized the payment. Now the Mr. Biden White House is planning to send out tens of millions of letters informing Americans about the benefits of the stimulus package and the checks it has sent to them.

Much of the public’s good feeling is driven by the decline of the coronavirus pandemic, which has been the main theme of Mr. Biden’s first 100 days. He has received sky-high public approval on his handling of the pandemic, and as businesses open up and restrictions ease, a boost of summer good will may be in store. Then again, with recent polls showing that about a quarter of adults nationwide don’t plan on getting vaccinated, scientists are now raising the possibility that herd immunity could become impossible.

Patrick Murray, the director of polling at Monmouth, said that the survey data pointed to trouble ahead for Mr. Biden. “We’re reaching this point of where we’re maxing out on the number of folks who are willing to get the vaccine,” he said. “The question is, does that lead to another surge? And in that case, it’s likely that those in charge, whether it’s the president or governors, are going to be blamed for this — because that’s what we normally do in that situation, rather than blaming ourselves for not abiding by the recommendation.”

This is all happening in a moment when American voters have put unity at the top of their agenda. In a separate Ipsos poll for Public Agenda and USA Today, nine in 10 Americans said that overcoming divisiveness was more important now than ever before. (Perhaps memories of the mid-1800s, and before, have faded a bit.)

Mr. Biden’s goal is to unify the public behind his agenda of reducing inequality and confronting the climate crisis, while bridging divisions within his own party. In the process he’s been willing to basically cast aside the Republican Party, which is caught up in internal warfare this week over whether to depose Representative Liz Cheney as its No. 3 in the House.

The stain of partisanship may be enough to at least slightly taint a president’s brand ahead of the midterm elections. Mr. Obama paid the price at the ballot box in 2010 in part because Tea Party activists were able to rally the Republican base by pointing out that Mr. Obama had passed his health care law without any meaningful G.O.P. support.

But so far, Americans appear more inclined to blame Republicans for the lack of cooperation than to blame the president. Two-thirds of respondents to the ABC/Ipsos poll said that Republican lawmakers hadn’t done enough to compromise with Mr. Biden; just 39 percent said Mr. Biden had done too little to compromise with them.

And Mr. Murray said that the overall climate of the country, and how much Mr. Biden had delivered, would go further toward determining his party’s success than bickering over bipartisanship. “If Biden is successful in getting these plans through and people feel that they’ve gotten some benefit from it, they don’t care how he passed it,” he said.

New York Times Podcasts

Sway: How Pete Buttigieg may try to win over Joe Manchin

On today’s episode, Kara Swisher was joined by Pete Buttigieg, the transportation secretary, to discuss his new role in the Biden administration, how the president’s $2 trillion infrastructure plan will tackle climate change, and the future of electric vehicles in the United States.

You can listen here, and read a transcript here.