Last weekend, the Republican presidential candidates addressed roughly 1,000 conservative activists at the Iowa Faith and Freedom Coalition. The crowd was overwhelmingly anti-abortion, anti-gay marriage, anti-illegal immigration, anti-taxes and anti-gun control. Yet those weren’t the issues the candidates talked about most. What they talked about most was the Middle East, and in particular, Israel. As Bob Vander Plaats, a prominent Iowa conservative, told National Journal, “Foreign policy is going to be a big issue for conservatives today. And the reason is because of what they see Obama doing with our relationship with Israel.”

Why do American conservatives care so much about Israel? The standard answer, especially among liberals, is theology. Many conservative evangelical Christians interpret the Book of Genesis as giving Jews control of the land of Israel and the Books of Daniel, Isaiah, Ezekiel and Revelations (in the Christian Bible) as requiring Jews to return there to hasten messianic times.

But while theology plays a role, liberals exaggerate it. For one thing, more secular conservatives are almost as pro-Israel as their fervently religious counterparts. A Pew Research poll earlier this year found that, “There are no significant differences in opinions of [Benjamin] Netanyahu by religious tradition among Republicans.” And even those conservative politicians who are overtly religious don’t generally justify their support for Israel in religious terms. In March, Texas Senator Ted Cruz launched his presidential campaign at Liberty University, a Christian institution founded by religious right leader Jerry Falwell. In his announcement speech, Cruz talked openly about “the transformative love of Jesus Christ.” But when he got to Israel, he didn’t cite the Bible. “Instead of a president who boycotts Prime Minister Netanyahu, imagine a president who stands unapologetically with the nation of Israel,” Cruz thundered. “Imagine a president who says ‘We will stand up and defeat radical Islamic terrorism and we will call it by its name.’”

The contrast between Israel and “Islamic terrorism” is key. Since the United States became a world power, conservatives have tended to define America’s mission as leading the West against some global, existential, civilizational foe. First it was the Nazis; then it was the communists; now it is “radical Islam.” The “West” is an amorphous, fluid concept: part geographic, part ideological, part cultural, part religious, at times even racial. But however they define it, American conservatives have long felt a special affinity for those Western outposts that define the frontier between them and us. During the Cold War, one such outpost was South Vietnam, whose government was not only anti-communist but led by a devout Catholic, Ngo Dinh Diem. Poland, a deeply Christian society resisting Soviet domination, was another. Taiwan was a third. In 2008, when Russia invaded Georgia, whose English-speaking President Mikheil Saakashvili had made his country a poster child for George W. Bush’s freedom agenda, Republican presidential candidate John McCain declared that “today we are all Georgians.”

Today’s conservatives love Israel for a similar reason. In this era, they believe, the West’s great enemy is “radical Islam.” And the West’s great outpost, on the frontlines against Islamic terror, is Israel. It’s modern; it’s democratic; it’s pro-American. And it’s under attack from the same forces that want to destroy the United States.

But there’s a twist. It’s not just that Israel represents the West. It’s that Israel represents the West at a time when many conservatives feel the United States no longer does. As the result of demographic change, the United States is become less Christian, less nationalistic and less white. And for many on the right, Barack Obama — a black man with a Muslim father who grew up in Indonesia and supposedly considers American power a bad thing — personifies this shift.

Netanyahu, by contrast, believes that America and Israel are utterly virtuous while our Islamic enemies are utterly evil. He, like Cruz, believes that the only problem with American power is that it isn’t wielded self-confidently enough. And thus, he represents the America that conservatives fear is slipping away. “In sad recognition that we can expect no such thing from our own president,” Weekly Standard editor William Kristol wrote in the days before Netanyahu’s speech to Congress, “we say to the prime minister of Israel: When you speak to Congress, speak for the West."

There’s an irony here. Conservatives love Israel for the same reason anti-Zionists hate it. Think about the words Israel’s harshest foes use to describe it: colonial, imperial, settler, apartheid. What they all convey is that Israel is a foreign creation, imposed by Europeans, and sustained by the United States, at the native population’s expense. For the American right, being a Western outpost in the Middle East makes Israel heroic. For the anti-Zionist left, it makes Israel illegitimate.

That’s why Israel has become so important to the American right. For many conservatives today, Western civilization isn’t only embattled in the Middle East. It’s also embattled inside the United States. Thus, the struggle over how America treats Israel is also a struggle over how America defines itself.