On Sunday’s broadcast of ABC’s “This Week,” President Donald Trump’s former homeland security adviser Tom Bossert said if Trump does not stop focusing on debunked 2016 election allegations, it will “bring him down.”

Partial transcript as follows:

STEPHANOPOULOS: We begin with President Trump’s first homeland security advisor, Tom Bossert, whose core responsibilities included election security and helping coordinate the U.S. government response to Russian interference in the 2016 elections. Tom, thank you for joining us this morning. You know, the whistleblower’s complaint says that White House officials were deeply disturbed by the president phone call with Zelensky. What was your reaction?

BOSSERT: Yes, I’m deeply disturbed by it as well and this entire mess has me frustrated, George. Thanks for having me on. You and I both lived through the impeachment of President Clinton and saw how frustrating and dividing it can be, and I’ve just spent a week overseas, and I’ll tell you, the whole world is watching this. The removal of a president is a — is a big and serious deal. But the removal of a president in not only a democracy but the biggest democracy in the world is really a weighty matter and I hope that everyone can sift through the evidence and be very careful, as I’ve seen a lot of rush to judgment this week. That said, it is a bad day and a bad week for this president and for this country if he is asking for political dirt on an opponent.

But it looks to me like the other matter that’s far from proven is whether he was doing anything to abuse his power and withhold aid in order to solicit such a thing. That seems to be far from proven and it’s going to be the focus of I think our Congress for the next year.

STEPHANOPOULOS: That’s the investigation. Let’s walk through some of what’s in the whistleblower’s complaint. And I want to show it up on the screen. It starts with President Zelensky saying “I’d really like to thank the president for your great support in the area of defense. We are ready to continue to cooperate for the next steps. Specifically, we are almost ready to buy more Javelins from United States for defense purposes.” And then the president says, “I would like you to do us a favor, though, because our country has been through a lot and Ukraine knows a lot about it. I would like you to find out what happened with this whole situation with Ukraine. They say Crowdstrike…I guess you have one of your wealthy people, the server they say Ukraine has it. There are a lot of things that went on. The whole situation.”

Now, what the president is referring to there is a debunked conspiracy theory that somehow Ukraine, not Russia, hacked the Democratic emails in 2016 and that Ukraine might have the DNC server or Hillary’s emails. The details are both convoluted and false. And during your time in the White House, you explained that to the president, right?

BOSSERT: I did. It’s not only a conspiracy theory, it is completely debunked. You know, I — I don’t want to be glib about this matter, but last year retired former senator Judd Gregg wrote a piece in The Hill Magazine, saying the three ways or the five ways to impeach oneself. And the third way was to hire Rudy Giuliani. And at this point I am deeply frustrated with what he and the legal team is doing and repeating that debunked theory to the president. It sticks in his mind when he hears it over and over again.

And for clarity here, George, let me just again repeat that it has no validity. United States government reached its conclusion on attributing to Russia the DNC hack in 2016 before it even communicated it to the FBI, long before the FBI ever knocked on the door at the DNC. So a server inside the DNC was not relevant to our determination to the attribution. It was made up front and beforehand. And so while servers can be important in some of the investigations that followed, it has nothing to do with the U.S. government’s attribution of Russia of the DNC hack.

STEPHANOPOULOS: Yet the president keeps on repeating it. You — you — you condemned Mayor Giuliani for continuing to tell the president (inaudible). How do you explain why the president brings this up in a meeting with the Ukrainian president? That is a form of pressure, isn’t it?

BOSSERT: Well, I didn’t see, like others have seen, pressure in this call. I understand why people are interpreting it that way. But I’ve spent a lot of time with this president, and I can easily see other reasons for why this president might have delayed the aide to Ukraine and those Javelin missiles. In fact, as you know, President Obama considered this deeply and decided not to provide lethal military support. President Trump and I and others spent quite a bit of time talking about this. In fact, in the call itself, although there are a lot of other reasons, he alludes to one that’s kind of quintessentially Donald Trump, and that is his frustration that Angela Merkel and the German nation member of NATO is doing nothing to help Ukraine, and — and he expressed some lamentation over that fact. So why he delayed is the key question. And — and — and you know, important, George, to remind everyone that he did ultimately provide the money and the Javelin missiles…

STEPHANOPOULOS: And that’s your…

BOSSERT: …but this was the second time that he considered doing it.

STEPHANOPOULOS: And that’s your judgment on whether or not it would be an impeachable offense. But on its face, requesting the Ukrainian president to investigate this debunk conspiracy theory and to investigate a political rival, that’s not appropriate for a president, is it?

BOSSERT: The DNC server and that conspiracy theory has got to go. They have to stop with that, it cannot continue to be repeated in our — in our discourse. On the other matter, I honestly believe this president has not gotten his pound of flesh yet from past grievances on the 2016 investigation. I believe he and his legal team have been looking into this, probably even prior to Joe Biden announcing that he would run for president. And they’re continuing to focus on everything they can, in their belief — understandably, in this case — that the president was wrongly accused of colluding with Russia the first time around. But George, if he continues to focus on that white whale, it’s going to bring him down. Enough. The investigation’s over. There was no evidence of collusion. He’s won and he should take that victory and move forward.