President Trump released a provocative campaign ad Saturday charging Democrats with being “complicit” in killings by immigrants who are in the country illegally.

The 30-second online spot posted to YouTube came on the first day of a partial federal government shutdown caused in part by Congress's disagreement over immigration policy. The ad, on the first anniversary of Trump's inauguration, was distributed to reporters in an email from Trump's campaign and purportedly featured scenes from the trial of an undocumented immigrant who was alleged to have killed two police officers in Sacramento.

“It's pure evil,” a narrator says. “President Trump is right: build the wall, deport criminals, stop illegal immigration now. Democrats who stand in our way will be complicit in every murder committed by illegal immigrants. President Trump will fix our border and keep our families safe.”

Trump nixed a bipartisan Senate proposal that would have provided legal status to immigrants who came to the country illegally as children, known as “dreamers,” in exchange for a $1.6 billion down-payment on his push to build a wall on the southwest border with Mexico. The plan also would have made changes to the nation's legal immigration system.

Without the immigration deal, the Senate blocked a House bill that would have funded the government for four weeks, leading to the shutdown. A large majority of Democrats voted against the bill, along with a handful of Republicans.

Trump has repeatedly sought to paint immigrants as dangerous, talking about transnational gangs, such as MS-13, and implementing a travel ban on travelers from some countries in the Middle East and Africa over what he said were concerns about terrorism.

But some studies have shown that immigrants, including those here illegally, commit crimes at lower rates than do native-born Americans.

For example, a March 2017 study by the pro-immigration Cato Institute found that “all immigrants are less likely to be incarcerated than natives relative to their shares of the population” and that “even illegal immigrants are less likely to be incarcerated than native-born Americans.”

As The Washington Post's Fact Checker reported in 2015, one study showed that between 1990 and 2013, “the foreign-born share of the U.S. population grew from 7.9 percent to 13.1 percent and the number of unauthorized immigrants more than tripled from 3.5 million to 11.2 million.

“During the same period, FBI data indicate that the violent crime rate declined 48 percent — which included falling rates of aggravated assault, robbery, rape, and murder. Likewise, the property crime rate fell 41 percent, including declining rates of motor vehicle theft, larceny/robbery, and burglary,” according to the American Immigration Council.

The violent crime rate was cut nearly by half during a period in which unauthorized immigrants tripled, according to the council.

Salvador Rizzo contributed to this report.