Refugee camps are another zone of indoctrination. They are full of vulnerable people, and Islamists prey on them. They come offering food, tents and first aid, followed by education. They establish madrassas in the camps, then indoctrinate the kids with a message that consists in large part of hatred for Jews and rejection of Israel.

Perhaps—I do not know—this is what happened to Ms. Omar in the four years she spent in a refugee camp in Kenya as a child. Or perhaps she became acquainted with Islamist anti-Semitism in Minnesota, where her family settled when she was 12. In any case, her preoccupation with the Jews and Israel would otherwise be hard to explain.

Spreading anti-Semitism through all these channels is no trivial matter—and this brings us to the question of resources. “It’s all about the Benjamins baby,” Ms. Omar tweeted in February, implying that American politicians support Israel only because of Jewish financial contributions. The irony is that the resources available to propagate Islamist ideologies, with their attendant anti-Semitism, vastly exceed what pro-Israel groups spend in the U.S. Since the early 1970s the Kingdom of Saudi Arabia has spent vast sums to spread Wahhabi Islam abroad. Much of this funding is opaque, but estimates of the cumulative sum run as high as $100 billion.