It was not a reassuring message. For many American friends of Israel, an agonizing political balancing act was ahead.

Eleven months later, the political situation appears both clearer and far more anguished.

The barbaric attack on Israel by Hamas militants last weekend summoned an outpouring of sympathy for Israel from across the American political spectrum. Democratic angst about the Netanyahu government seemed to disappear — and, suddenly, the composition of Israel’s leadership changed as the opposition politician Benny Gantz joined Netanyahu in an emergency war government.

What is not clear is how long this spirit of pulling together might last in America’s varied and strained pro-Israel community. Within days or even hours, the impulse to lock arms with Israel could be challenged by the country’s promise of unforgiving retaliation against Hamas and the consequences of a military campaign for Palestinian civilians in Gaza and elsewhere. Already, progressive lawmakers have begun urging the Biden administration to do more to restrain Israel’s military response.

When I spoke with Mellman on Friday, he said this moment had brought a kind of awful moral definition to the politics of the Democratic Party, likening it to previous invasions of Israel that shifted American public opinion.

“The savagery of Hamas has moved the center of gravity in a pro-Israel direction,” Mellman said. “This is a redefining moment in the same way that ’67 and ’73 were redefining moments.”

It is a core trait of American progressives to identify with communities they perceive as vulnerable and disempowered and often to interpret foreign conflicts in those terms. Mellman suggested that the attack could resonate with particular effect among liberal Americans who tend to see the world in terms of “victims and oppressors.”

“The reality is, people are seeing thousands of Israeli families as victims today, and that’s a very different picture than some of those folks had just last week,” Mellman said, adding: “That’s going to be tested, obviously, as Israelis move from being victims to trying to end Hamas’ rule in Gaza.”

Even in this moment of relative unity, Israel faces two profound political challenges in the United States.

The first and better understood one is the growing suspicion of the country among younger and more liberal Americans. They are likelier than their parents and grandparents to see the Palestinian cause as just and morally urgent. Few of them remember a time when there was an active and promising peace process, or when Netanyahu’s name was not virtually synonymous with the Israeli state. These generational trends are not on Israel’s side.

The second, perhaps more dangerous, problem for Israel is American voters’ default indifference to the rest of the world.

The biggest American threat to Israel may not be that the pro-Palestinian left wins a grand policy debate that shifts regional politics on its axis, but rather that most Americans forget that they are even supposed to care about that debate. We are already well past the post-9/11 phase of U.S. politics in which most of the country saw the Israeli fight for long-term security and the American struggle with Islamic terrorism as synonymous. Is it possible that within a decade or two, most Americans might react to a brutal attack on Israel with the same shoulder shrug they gave to Azerbaijan’s recent blitzkrieg against Armenia?

The polling this week is instructive. A YouGov/Economist survey found a jump in support for Israel following the Hamas rampage. The share of Americans saying they sympathized more with Israelis than with Palestinians rose by 11 points — from 31 percent in March to 42 percent now. That is a pronounced change, but still something short of overwhelming concern.

Just as suggestive is the reaction to the attack within the GOP — ostensibly the party that feels less ambivalence about Israel.

Amid an outpouring of support for Israel across party lines in Washington, Donald Trump at first largely ignored the attack and then trashed Netanyahu in personal terms at an event in South Florida. Several of Trump’s opponents, including Ron DeSantis and Mike Pence, rebuked him. But he does not seem likely to pay a political price for his comments; many conservative voters may feel kinship with Israel but not to the point of letting it affect their more passionate love for Trump.

For anyone who thinks it is outlandish to suggest conservatives might stop caring about Israel altogether, consider how recently it was unthinkable to imagine Republicans might lose interest in securing Eastern Europe from Russian aggression.

What American supporters of Israel need is a new political story — one that is neither anchored in nostalgia for a 20th century version of the country nor one that draws on a Bush-era spirit of unity and crusade. Those are the political currents that have drawn Netanyahu and Biden together, again and again, despite their differences. For many voters they are losing force, similar to what has happened with Cold War-style rhetoric about restraining Russia.

Too many American politicians have tried for too long to talk around the most vexing elements of Israel’s identity: the rifts in culture, religion and politics that have destabilized the country; the power of radical right-wing factions and settler movements; the refusal to address the suffering of ordinary Palestinians in a responsible way. American leaders have assumed (perhaps rightly) that voters can’t be counted on to process the nuances of the world.

That is not a sustainable arrangement. Appeals that are anchored in evasion and elision cannot hold up over time. Supporters of Israel need to figure out how to acknowledge to American voters what Israel is — a vibrant, resilient, alarmingly polarized society that shares many American values but not all of America’s interests — and persuade them to regard it as an especially important country all the same.

The long-term viability of that political project may depend on what happens on the ground in Israel in the next few weeks.

I asked Mellman on Friday if he worried that Americans could lose interest in Israel over time — that voters here could come to see violence there with the same shallow and short-lived empathy that they feel for victims of natural disasters in far-off places. He did not sound as concerned as I am about that precise scenario.

“This is a situation that doesn’t disappear,” he countered. “For better or worse, the Middle East will be with us on a continuing basis.”

Mellman acknowledged more uncertainty about whether the present mood of solidarity would hold — and whether American liberals would continue to embrace Israel as so many of them have done for the last week.

“That redefinition is at some risk with some people because of what is about to happen in Gaza,” he said. “But I think there has been a fundamental shift.”