In October 2019, a whistleblower anonymously complained that U.S. President Donald Trump, his lawyer Rudy Giuliani, and other high-ranking Trump administration members had made phone calls with Ukrainian president Volodymyr Zelensky, asking him to have the Ukrainian government investigate Joe Biden, who was a candidate in the 2020 Democratic primaries at the time; as well as his son Hunter Biden in exchange for keeping U.S. military aid to Ukraine going. The complaint raised concerns that Trump was asking for other countries to interfere in the 2020 presidential election.