Mr. Biden’s polling numbers have been mired in dangerous territory since he oversaw the chaotic American military withdrawal from Afghanistan. The enactment of popular legislation on infrastructure and renewable energy investments has done little to improve his popularity. A White House push to promote economic improvements under the banner of “Bidenomics” has done little to convince voters of its merits.
“I don’t anticipate any long-term benefits politically,” Julian E. Zelizer, a professor of political history at Princeton University, said of Mr. Biden’s handling of the war in Israel. “We live in an era now where polarization is so deep that no matter what the magnitude of the crisis is, or the performance of the president, it’s not likely to make a difference.”
Several voters interviewed on Friday were skeptical of Mr. Biden’s call to send $14 billion to help Israel — let alone another $60 billion for Ukraine.
Samantha Moskowitz, 27, a psychology student at Georgia Gwinnett College in the Atlanta suburbs, said the prospect of sending billions to Israel and Ukraine “makes me anxious, especially where our economy is right now.”
“I don’t love the idea that the money is being sent,” said Ms. Moskowitz, who did not vote for either Mr. Biden or Donald J. Trump in 2020 and said it was “too early to tell” if she would vote in 2024. “There is a need, but do we really need that significant amount?”
She said she did not watch Mr. Biden’s Oval Office address on Thursday.
About 20.3 million people watched Mr. Biden’s speech across 10 television networks, according to preliminary data from Nielsen. The total audience for the speech was certainly bigger, given that the Nielsen data does not capture some online viewing numbers.
When Mr. Trump spoke about immigration from the Oval Office in January 2019, about 40 million people tuned in. Just over 27 million people watched Mr. Biden’s State of the Union speech in February.
Stanley B. Greenberg, who was Mr. Clinton’s pollster in 1992, called Mr. Biden’s Oval Office address “a very important speech in terms of defining America’s security and bringing Iran and Russia to the forefront,” and predicted that it could help rally voters around the president and push Congress to pass his $106 billion international aid plan, which includes money for Ukraine and the Middle East.
“Of course, a year from now, voters will be voting on the cost of living, the economy, the border, crime and other issues,” he said. “Foreign policy is rarely a voting determinant, but President Biden may be leading the attack on isolation and a new partisan choice on how we gain security.”
The initial polling suggests that broad majorities of Americans endorse Mr. Biden’s staunch support for Israel. A Fox News poll found that 68 percent of voters sided with Israel, and 76 percent of voters in a Quinnipiac University poll said that supporting Israel was in the national interest of the United States.
With the exception of 2004, when President George W. Bush confronted rising criticism about having led the nation into war against Iraq, no national election has been driven by foreign policy since the end of the Vietnam War.
The nature of the presidential campaign could change if the conflict in Israel continues to dominate the news for weeks and months. Unlike the elder Mr. Bush after the 1991 Iraq war — which began and ended quickly with what at the time seemed a clear victory — Mr. Biden could be presenting himself as a wartime president through the course of his re-election bid, a prospect that also carries political risks.
Mr. Biden’s support for sending military aid to Israel, even accompanied by gentle pleas to the country’s leaders for restraint, has alienated many on the left wing of his party, who point to a high Palestinian death toll in Gaza that is likely to rise as Israel presses its offensive.
This week, thousands have marched on the Capitol amid a series of open letters — including one from a long roster of former presidential campaign staff members for Senator Elizabeth Warren of Massachusetts — demanding that Democratic lawmakers urge Mr. Biden to push for a cease-fire in Israel, which he is unlikely to do.
The president has picked sides in a conflict over which he has little control. Most immediately, Mr. Biden faces the challenge of what he can do to secure the release of Americans being held hostage in the Gaza Strip. Hamas released two American hostages on Friday afternoon, and Secretary of State Antony J. Blinken said that 10 more Americans had yet to be freed.
Dr. Zelizer said, “I think the assumption should be that things will go south and there will be detrimental effects.” Referring to Mr. Biden and his administration, he added, “There’s assistance, but they don’t have real control over how this unfolds.”
For all of those risks, these next few months may give Mr. Biden a window to shake up the contest in ways that could put him on firmer ground.
“It gives him an opportunity to change and strengthen his image,” said Charles R. Black Jr., a strategist for the presidential campaigns of both Bushes and Ronald Reagan. “It gives him a chance to demonstrate his strength and also his knowledge.”
Paul Begala, a Democratic consultant, said that this political moment could prompt voters to give Mr. Biden a second look. “The fear with an incumbent president is that voters write you off, they stop listening,” he said.
“What’s the biggest thing about Biden?” Mr. Begala added. “Old. This gives him a chance to lean into it. I don’t think people are going to vote on how he does in Israel. But I think this can let them reframe the age problem. It is a way for people to look and say, maybe it’s good we have the old guy in there. He is steady and strong.”
For Mr. Biden, an orderly handling of the crisis would be likely to buttress what is expected to be another dominant theme of his campaign if he finds himself running for a second time against Mr. Trump, with turmoil continuing among House Republicans as they seek to elect a speaker.
“Hopefully the House chaos will calm down long before the election,” Mr. Black said. “But Trump is so ad hoc on foreign policy that it’s always chaos.”
John Koblin contributed reporting from New York, and Sharon Dunten from Norcross, Ga.