President Donald Trump's former homeland security adviser slammed the president's lawyers and associates for continuing to tout debunked conspiracy theories in an effort to insulate the president and boost his political standing.

Tom Bossert slammed Trump and his longtime lawyer Rudy Giuliani for echoing debunked conspiracy theories about the hack of the Democratic National Committee computer servers during the 2016 election campaign in an effort to curry favor for the president in a turbulent administration.

Bossert pointed to Trump's legal team's insistence that the president had done no wrong and was in fact a victim, which he said is repeated to the point that "it sticks in his mind when he hears it over and over again," even though it has "no validity."

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President Donald Trump's former homeland security adviser slammed the president's lawyers and associates for continuing to tout debunked conspiracy theories in an effort to insulate the president and boost his political standing.

Tom Bossert said on "This Week With George Stephanopoulos" Sunday that he was "deeply disturbed" and "frustrated" by the "entire mess" that has broken out over Trump's phone call with the Ukrainian president that is at the center of a whistleblower complaint and a surge of calls for his impeachment.

He specifically took aim at Trump and his longtime lawyer Rudy Giuliani's repeated echoing of debunked conspiracy theories about the hack of the Democratic National Committee computer servers during the 2016 election campaign in an effort to curry favor for the president in a turbulent administration.

"It's not only a conspiracy theory, it is completely debunked," Bossert said. "I don't want to be glib about this matter but last year, retired former Senator Judd Gregg wrote in The Hill ["How to Impeach Oneself"] and the third way was to hire Rudy Giuliani."

Bossert pointed to Trump's legal team's insistence that the president had done no wrong and was in fact a victim, which he said is repeated to the point that "it sticks in his mind when he hears it over and over again," even though it has "no validity."

The administration's clash with former Vice President and Democratic 2020 hopeful Joe Biden has been years in the making, Bossert said, pointing to the thinking inside the administration that is still seeking to right a wrong against Trump.

"I honestly believe this president has not gotten his pound of flesh yet from past grievances on the 2016 investigation," Bossert said. "I believe he and his legal team, probably even prior to Joe Biden announcing that he would run for president, have been looking into this and are continuing to focus on...that the president was wrongly accused of colluding with Russia the first time around."

Bossert said Trump's fixation on wrongdoing in the 2016 election is counterproductive after a special counsel investigation found that there was no evidence of his collusion with a foreign government.

"If he continues to focus on that white whale, it's going to bring him down," Bossert added. "Enough. The investigation is over, there's no investigation of collusion, he's won and he should take that victory and move forward."

Bossert previously served as deputy homeland security adviser to President George W. Bush and was known in his year with the Trump administration as a firm defender of Trump and a trusted advisor on terrorism, cybersecurity issues, and natural disasters.

His recent comments come as something of a surprise for the former loyal Trump adviser who was even at the center of some of the president's well-known controversies, as he was criticized for defending the president's comments on issues like white supremacist protesters in Charlottesville, Virginia in 2017 and Russian interference in the 2016 election.

Some of Bossert's comments made while he was in the administration seemed in contrast to his sharp dismissal of the president's concerns about the 2016 election, including when he said in 2018 that "no voter in this country was influenced" by Russian bots during the election.

"I honestly do believe that there is a large degree of misunderstanding in the reporting and there's a whole lot of attempted politicking going on meant to try to undermine the legitimacy of the election," he told NBC News in April 2018.

The presidents' inner circle has come under harsher scrutiny as House Intelligence Committee Chairman Adam Schiff said last week that his committee is mapping out potential hearings, depositions, and subpoenas ahead of an impeachment probe.

Multiple polls have indicated growing public support for impeachment, adding a swell of support as Democratic lawmakers take aim at key figures in Trump's circle.