Biden’s real reelection problem isn’t his age. It’s his waning popularity.

After the war between Israel and Hamas broke out, a war in which thousands of innocent Palestinians and Israelis have died, Biden immediately flew to Israel. This was only the second time a sitting president in American history had traveled into an active war zone — the first time was also Joe Biden’s, after he rode a train for 10 hours, under cover of night, from Poland to Kyiv last winter. In terms of stamina, Biden’s ability to endure days of stress to tend to a crumbling international order may eviscerate the critics’ argument that he’s too old to be president.

In fact, I think Biden’s age is a virtue, given his experience and wisdom. His problem now runs much deeper.

The question going forward is not whether Biden is too old — it’s whether he’s too unpopular, especially among the young who will form the backbone of the Democratic Party in 2024 and beyond. A great fracture is forming in Biden’s progressive coalition. The president has a dismally low approval rating of 37 percent overall and only 75 percent among Democrats. It is an irony and growing tragedy: On domestic policy, Biden has presided over one of the most substantive and forward-looking administrations in American history, with the most significant legislation on energy and infrastructure ever. But on foreign policy generally and the Israeli bombardment of Gaza specifically, Biden has not yet demonstrated that America’s actions match up with its ideals, or that he has any vision for an American-led peace in the world. This could mean that he loses next year and takes American democracy with him.

Under normal circumstances, Biden’s achievements on domestic policy alone would make him worthy of reelection. But we live in unique and uncertain times. The 2024 race, as I have argued before in these pages, will be a foreign policy election.

And now war in the Middle East threatens to draw America into another prolonged regional conflict. Going to war with Iran would be so disastrous for the world that the Iraq War would seem minor. Americans are right to question where this war in Gaza is heading and whether Biden is making the right calls for future generations. After Biden supplied weapons and warships to Israel and downplayed the number of innocent Palestinians killed in the war, many progressives, including Arab and Muslim organizations, began explicitly questioning whether to support him in 2024. These voters will be critical in swing states like Michigan, which Biden won by less than 155,000 votes.

The anger toward Biden on the left is sincere. One progressive organizer summed up the frustration of American progressives toward the Biden administration by telling The Washington Post: “Are we dealing with warmongers or are we dealing with peacemakers? Who are we dealing with?”

Indeed, Biden’s coalition seems more fragile than ever — and making sure his own voters are not exhausted and apathetic will be the biggest factor in defeating Donald Trump. Biden’s inability to channel the genuine frustrations of progressive voters might cost him the election — just like it cost Hillary Clinton in 2016.

Young voters may bring the worst news for the president’s reelection prospects. A recent Quinnipiac poll found that among voters under the age of 35, Biden’s favorability has tanked to an unprecedented low of 25 percent.

As a Millennial, I believe I have some insight into what’s going on. The young are fiercely committed to the cause of social justice; they are less accepting of received ideas or dictates and prefer to see things fresh and outside the boxes proffered by elders. Today’s young are the post-9/11 generation, the ones who grew up losing some part of their childhood to the aftermath of the War on Terror, and what unites them is a revulsion toward wars and an unquestioning supply of US arms to enable more bloodshed. These aren’t debaters’ points — America’s young today are genuinely committed to repairing the world. They rightfully question why they, who will have to live longest with the consequences of today’s wars, are not heard. Young voters will ask, “If a Biden presidency means a world in flames, why bother voting?”

Biden’s age and experience should give him the credibility to break with the Washington consensus and apply pressure for peace in the Middle East. The president has posited that America is an indispensable nation, a shining beacon of opportunity. Yet he has not even attempted to answer the corollary: If American power is so great, if it can bend the arc of the moral universe, why not bend it toward peace?

The irony is that Joe Biden is indisputably the most progressive president in recent times. He helped usher through Congress the three most consequential pieces of legislation in a generation: the CHIPS Act, which invests in domestic semiconductor design, research, and manufacture; the Inflation Reduction Act, the single largest investment in climate and energy in American history; and the Bipartisan Infrastructure Law, an unprecedentedly large investment in transportation. The revitalization of America’s infrastructure, so long overdue, could unleash a new wave of productivity and American building — what this country was once good at.

If there is an apt comparison for the Biden presidency, in policy and in substance, the only administration that comes to mind is that of Franklin Delano Roosevelt. FDR is someone Democrats could champion a little more, given that he passed the New Deal, saved the American economy, created Social Security, created the National Labor Relations Board, and helped usher in the American century. He blunted the edges of capitalism and so dulled the appeals of extremism. Roosevelt was also sick for most of his presidency. He used a wheelchair, and his handlers positioned the photographers so Americans never learned the true extent of FDR’s illness.

FDR’s internment of Japanese-Americans, to be clear, is a cautionary tale about what even liberal presidents are capable of when racism takes over. But Roosevelt defeated fascism and won four terms. His overall legacy is one of supporting universal liberal democracy and helping to build a world where barbaric wars were mediated by diplomatic compromise, a planet where all could be free from want and fear.

What is Biden’s vision for this century? How will the United States play an active role in peace? He is speaking the language of idealism but, in supplying arms to Israel without pre-conditions, has engaged in militarism. Biden could wield US power to limit the civilian toll of Israel’s bombardment of Gaza. He could pressure Israel to end settlement expansion and settler violence in the West Bank. He could restate America’s commitment to a Palestinian state, which, even before this war, Biden had not emphasized. Absent a resolution of Palestinian statehood, the fundamental issues will be delayed for another war. What is Biden’s vision for the aftermath of this war?

Being more like Franklin Roosevelt means elevating the principles of diplomacy and power to secure peace. It also means directly speaking to the American people the way FDR did. Biden hardly talks to Americans and rarely speaks directly to the young. He is effectively pushing away the very people who supported him in 2020 and will be crucial to next year’s election. Biden should unapologetically champion his progressive agenda — as he did when he went to the picket line with striking autoworkers. Biden should also be holding fireside chats every week from the Oval Office, live-streamed right on social media where he explains, in his folksy way, how his agenda will help ordinary people.

At a time of transition and chaos, an experienced hand like Biden’s is needed in the White House. But to win a second term, he’ll have to present a clear, affirmative vision to young people that gives them hope. Otherwise, Joe Biden — and American democracy — may suffer a loss from which recovery is impossible.

Omer Aziz is the author of “Brown Boy: A Memoir” and a recent Radcliffe Fellow at Harvard University.