John Bolton: Trump directly linked Ukraine aid to Biden investigation

Former national security adviser John Bolton defended in an interview with ABC News on Sunday his decision not to testify at President Trump's impeachment inquiry, claiming it wouldn't have changed the outcome.

Why it matters: Bolton told ABC News that Trump "directly linked the provision of that [security] assistance with the investigation" into former Vice President Joe Biden and his son Hunter Biden in Ukraine — the central allegation that saw him impeached in the House and later acquitted in the Senate. No official that testified was a direct witness to Trump explicitly tying aid to the investigations.

What he's saying: "I didn't think the Democrats had the wit or the political understanding or the reach to change what, for them, was an exercise in arousing their own base, so that they could say, 'We impeached Donald Trump.' To impeach him on the ground of Ukraine, knowing full well — they could see it, they knew it from their own behavior," Bolton said in the interview with ABC's Martha Raddatz.

"They pushed the Republicans in the House into unanimous opposition to their view. And they essentially did the same thing to Republicans in the Senate. This was a partisan play. It was not a Constitutional process. I judge that to be almost as irregular as what they were accusing Trump of doing.

"The Democrats can pursue whatever policy they want. They don't dictate to me how best to bring this to the attention of the American people. You can agree or disagree with the way I tried to do it, but I don't think anybody is required to engage in futile activity to satisfy the Democratic congressional leadership."

Flashback: In January, Trump tweeted: "I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens. In fact, he never complained about this at the time of his very public termination. If John Bolton said this, it was only to sell a book."

Go deeper: Trump whacked from within by John Bolton

Editor's note: This article has been updated with more details from Bolton's interview and further context.