Former homeland security adviser says he warned Trump that Ukraine conspiracy theory was debunked

President Trump's first homeland security adviser said on Sunday that he told Trump on multiple occasions that a conspiracy theory about Ukraine meddling in the 2016 election was "completely debunked."

While appearing on This Week with George Stephanopoulos, Thomas Bossert said he was "deeply frustrated" that Trump's personal lawyer, Rudy Giuliani, and others outside the administration were "repeating that debunked theory to the president. It sticks in his mind when he hears it over and over again, and for clarity here ... let me just repeat that it has no validity."

During a July 25 call with Ukrainian President Volodymyr Zelensky, Trump not only asked Zelensky to launch an investigation into former Vice President Joe Biden and his son, Hunter Biden, but to also look into the conspiracy theory that it was Ukraine, not Russia, that was responsible for the Democratic National Committee hacking. Bossert said he was "deeply disturbed" by the conversation, and several former Trump aides told The New York Times it didn't matter how many times Trump was told that this theory was debunked, he wouldn't listen.

Multiple aides said Trump was more open to listening to Giuliani and other outsiders rather than his national security team, with one telling the Times that Giuliani would "feed Trump all kinds of garbage," which created a "real problem for all of us." Read more at The New York Times.