Khizr Khan, the father of a slain Muslim Army captain who gained national attention by pointedly criticizing former President Donald Trump during the Democratic National Convention in 2016, announced in an exclusive interview with NBC News that he is endorsing Vice President Kamala Harris’ presidential campaign and plans to act as a campaign surrogate for her.

In 2016, Khan denounced Trump’s treatment of Muslims and other minorities while holding a pocket-sized U.S. Constitution and challenging Trump to read the document. In his interview with NBC News on Saturday, Khan said Trump has “gotten worse” and that he fears the former president will become a dictator and end democracy as Americans know it.