On Monday evening, President Donald Trump took the opportunity to post a fear-mongering tweet about criminals and unknown Middle Easterners seeking to enter the United States in a migrant caravan.

The tweet, debunked as baseless even by Trumps own administration , has alarmed advocacy groups with its blatantly xenophobic, Islamophobic and anti-immigrant nature.

Its playing on peoples fears, said Abed Ayoub, the legal and policy director at the American-Arab Anti-Discrimination Committee , a civil rights organization based in Washington, D.C. It is looking at our community, the brown communities, the black communities, the Arab communities all of us through the same lens as a threat to our national security.

With the November midterms just around the corner, other politicians are following Trumps lead and appealing to bigotry for votes.

Its just a racist and Islamophobic dog whistle that he knows will work because its worked for him in the past, Ibrahim Hooper, the national communications director at the Council on American-Islamic Relations, told HuffPost.

The president has a lengthy history of making Islamophobic comments and propagating anti-immigrant hysteria. He called Latinos criminals and rapists and said Muslims were not assimilating and wanted sharia law to take over the U.S.

The latest controversial tweet appeared after several right-wing sites known for promoting Islamophobic conspiracy theories, such The Daily Caller and Judicial Watch, speculated that Bangladeshis had joined the migrant caravan currently crossing through Mexico toward the United States. (Bangladesh is not part of the Middle East, and its not clear why this would matter whether its true or not.)

Regardless of the facts, Trumps tweets are an attempt to rally public support for his immigration policies by telling a story that promotes fear, said Faiza Patel, co-director of the Liberty and National Security program at the Brennan Center.

This is a continuation of his strategy of painting Muslims and Middle Easterners as a security threat despite all the evidence to the contrary, Patel said. Its a lot easier to do that if you can portray everybody outside the country as being a threat or at least having a threat mixed in with them.

Advocates and civil rights groups are concerned about the potential effect of Trumps tweets. This is going to further alienate our communities and cause division as a result of his words and policies, Ayoub said. Its going to lead to additional scrutiny, hate crimes, harassment and discrimination.