Amid growing outrage over his administration's policy of separating migrant families crossing the U.S. border, President Donald Trump on Saturday pretended that it wasn’t his problem, and suggested the blame should lie with Democrats. “Put pressure on the Democrats to end the horrible law that separates children from there [sic] parents once they cross the Border into the U.S.,” he tweeted. “Catch and Release, Lottery and Chain must also go with it and we MUST continue building the WALL! DEMOCRATS ARE PROTECTING MS-13 THUGS.”

Like many things Trump tweets, however, the idea that Democrats are responsible for what is happening at the border is nonsense. As the Associated Press notes, the previous “catch and release” policy Trump and his administration cite as the reason for increased border crossings was put into place in 2008 by then-president George W. Bush, and was primarily created to combat the influx of children fleeing to the U.S. from Central American countries due to a surge of child trafficking. Under Trump, however, that policy has changed. In the past, the Office of Refugee Resettlement traditionally placed unaccompanied minors—that is, children who cross the border without a parent—in government-run detention centers. If a parent and a child came together, they would be processed together. In recent months, however, the Trump administration has begun forcibly taking children from their parents—some as young as one year old—and warehousing them in facilities far away from their parents, as if they had crossed the border alone.

The new policy has seen about 700 children separated from their parents since October, and the problem is only getting worse. A HuffPost report shows that the O.R.R. is already struggling with the number of refugees in its custody, and has struggled to keep track of where many of them have been placed. The office has already lost about 1,500 children, a Health and Human Services official revealed last month:

Until recently, families that illegally crossed together generally faced deportation proceedings in civil court. But as of this month, the Trump administration is following a blanket policy of referring for prosecution all people who cross illegally. The change means that authorities send parents to jails run by the U.S. Marshals Services and their children wind up in the same agency as minors who came to the U.S. without their parents―sometimes without their parents being able to locate them.

Despite Trump’s attempts to shift blame for these bad headlines to Democrats, the policy is all his own. As Chief of Staff John Kelly told NPR in an interview three weeks ago, the plan to forcibly separate mothers from their children was explicitly designed as a “tough deterrent” to scare immigrants from trying to enter the U.S. “The children will be taken care of—put into foster care or whatever,” he said flippantly. “But the big point is they elected to come illegally into the United States and this is a technique that no one hopes will be used extensively or for very long.” He also implied that those who wished to come across the border were “overwhelmingly rural” people who would find assimilating into the U.S. difficult. “They don’t speak English. They don’t integrate well. They don’t have skills.”

Under Obama, the Department of Homeland Security prioritized the deportation of people who had committed serious crimes, allowing most other undocumented immigrants to remain in the shadows. The DACA program allowed hundreds of thousands of undocumented immigrants who were brought to the U.S. as children to apply for temporary legal status. Last year, Trump rescinded that program. According to CNN, arrests of immigrants without criminal convictions have gone up substantially.