President Donald Trump may not believe that white nationalism is a growing threat, but Democratic Rep. Ilhan Omar thinks he has one in his ranks.

Omar tweeted Monday that Stephen Miller, one of President Trump’s top advisers, is a “white nationalist.”

Miller, a far-right political activist, has reportedly masterminded some of the Trump administration’s most aggressive immigration moves, such as the now-defunct “zero tolerance” policy, which separated children from their parents at the U.S. southern border.

“Stephen Miller is a white nationalist,” Omar wrote on Twitter. “The fact that he still has influence on policy and political appointments is an outrage.”

Omar linked to a piece from Splinter about Miller’s reported attempts to dismiss high-ranking officials within the Department of Homeland Security (DHS) because they weren’t hard-line enough on immigration. The former Secretary of Homeland Security, Kirstjen Nielsen, said Sunday that she would resign from her position. She had reportedly pushed back on the president’s wishes to reinstate family separations, and Miller called her “too weak” to handle the position.

With Nielsen gone, Miller is expected to push for a more hard-line crackdown on immigration.

Omar, one of two Muslim women ever elected to Congress, has repeatedly criticized Israel and its relationship with the U.S., and she supports the Boycott, Divestment, Sanctions (BDS) movement against Israel’s human-rights abuses in occupied Palestinian territories. Her outspokenness has caused several controversies and even led her opponents to paint her as anti-Semitic. (Her supporters, however, have dismissed the accusations as nothing more than attempts to silence any criticism of Israel.)

Trump supporters, including the president’s son, have joined in on the name-calling against Omar. And during a House Judiciary Committee hearing Wednesday on rising white nationalism, ranking member Rep. Doug Collins, a Georgia Republican, took an indirect swipe at her.

Omar’s stances on Israel have also led to multiple death threats against her. Last week, the FBI arrested a man who allegedly threatened to shoot Omar in the head and likened her to a “terrorist.” The man identified himself as a Donald Trump supporter.