Some Democrats, including Robert Reich, who served as secretary of labor in the Clinton administration, compared the spot to the 1988 "Willie Horton" ad, which supporters of Republican then-candidate George H.W. Bush used to great effect against Democratic rival Michael Dukakis. Critics slammed the video as racist.
According to the Washington Post, Luis Bracamontes, the man in the trial footage, was deported twice and ultimately given the death penalty in 2014 for murdering two police officers in California.
Bracamontes, an immigrant living in the country illegally, sports a shaved head and long chin hair and speaks in accented English in the video, and his words are clear: He's killed cops and he's "gonna kill more cops soon". "Illegal immigrant, Luis Bracamontes, killed our people!" reads text on the ad, which shows an unrepentant Bracamontes smiling in court and promising to kill more officers if he gets out.
The ad then turns to footage of the caravan of Central American migrants making their way towards the United States border.
"It is outrageous what the Democrats are doing to our Country", Trump tweeted with the video. Horton, who was black, raped a woman while out of prison on a weekend furlough.
For instance, Mitt Romney - who hired the team behind the Horton ads in his 2012 campaign against Barack Obama - was accused of playing into similar racial fears in advertisements attacking the president's health care and welfare policies.
"This may be the most desperate and vile ad since Willie Horton", Reich said on Twitter.
On the right, Jamie Weinstein of the conservative National Review tweeted Wednesday that the Bracamontes video was "without question. a racist ad". Trump provides no evidence linking Democrats to Bracamontes.
"This ad, and your full approval of it, will condemn you and your bigoted legacy forever in the annals of America's history books", Al Cardenas, the Florida Republican Party's former chairman, wrote on Twitter. "Your job is to make Mr Trump very, very nervous".