Trump's top Russia official quit the day before his impeachment testimony, and is looking like the most damaging witness yet

Jonathan Ernst/Reuters

President Donald Trump listens during a bilateral meeting with with Ukraine's President Volodymyr Zelensky on the sidelines of the 74th session of the United Nations General Assembly (UNGA) in New York City, New York, September 25, 2019.

• Tim Morrison, a senior White House director on Europe and Russia, announced his resignation Wednesday, the day before his testimony in ongoing impeachment hearings.
• Morrison is already part of the impeachment narrative: Last week acting Ukraine ambassador Bill Taylor described conversations with Morrison that helped convince him that President Donald Trump did indeed offer a "quid pro quo" exchange to encourage Ukraine to investigate Joe Biden.
• Sources close to Morrison last night described the timing of his departure as "notable" to Politico. Outside of a White House role, Morrison may find himself at greater liberty to speak.
• Trump and his team are desperate to argue that there was no "qui pro quo" arrangement. This is becoming increasingly difficult to maintain. Morrison's testimony will likely make it harder still.
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The White House's top Russia official quit on Wednesday - an auspicious move the day before testifying to lawmakers in the impeachment investigation into President Donald Trump.

Tim Morrisson, a senior White House director on Europe and Russia, announced his departure on Wednesday night - and there is reason to believe that the now ex-staffer's testimony will heap yet more trouble upon the president.

Morrison's testimony Thursday - based on what others have said about his involvement - seems likely to further erode Trump's main defense from allegations that he abused the power of his office to create political trouble for Joe Biden.

Trump and his lawyers have claimed that a conversation Trump had with his Ukrainian counterpart - where he asked Ukraine to probe Biden - was not an impeachable offense because there was no explicit offer (a "so-called quid pro quo) of actions by the US government in exchange.

Morrison did not go into details in a statement announcing his resignation, but the timing is unlikely to be good news for the White House.

In comments to Politico, sources close to Morrison said his departure had been planned for a while, but described the timing as "notable."

Morrison seems to have been at the center of events that led a whistleblower to raise the alarm about the president's pressure campaign against Ukraine, and the Democrats to probe a possible impeachable abuse of power.

Morrison took up his White House role about a year before the July 25 phone call in which President Donald Trump requested Ukrainian President Volodymyr Zelensky to launch a Biden probe.

Democrats want to know whether, in conversations with top US officials like Morrison, Trump made US military aid to Ukraine explicitly conditional on the country agreeing to probe Biden.

In testimony before House Democrats last week, acting Ukraine ambassador Bill Taylor laid out a forensic account, suggesting that the White House sought to leverage the roughly $400 million in yearly aid Ukraine relies on, in exchange for political favors.

Alex Wroblewski/Getty Images

Bill Taylor, the top U.S. Diplomat to Ukraine, leaves Capitol Hill on October 22, 2019 in Washington, DC

And at the center of his testimony was his account of two conversations with Morrison.

Taylor told lawmakers that Morrison relayed to him a conversation between Gordon Sondland, the US ambassador to the EU, and Andriy Yermak, a top aide to Zelensky.

According to the account of the conversation provided to Taylor, Sondland told the Ukrainian official that military aid would be witheld until Burisma, the Ukrainian energy firm where Hunter Biden worked, was investigated.

Morrison, being one step closer to the initial exchange, may be able to shed more light on it.

The second conversation involving Morrison could also prove pivotal: According to Taylor, Morrison also told him of experiencing a "sinking feeling" after learning of a different exchange involved Sondland - between Sondland and Trump - in which the president demanded that Zelensky announce a public investigation into Biden.

Morrison said that in the same exchange, Trump made the seemingly contradictory claim that there was no quid pro quo.

If Morrison corroborates or expands on these accounts, Trump's "no quid pro quo" defense will likely be left looking even more shaky.

The White House has tried to prevent staff from appearing in the hearings - regardless of whether his departure was planned, Morrison has now distanced himself from any professional pressure.

As ever, the specifics will depend on the testimony itself - but ahead of the hearing, it looks like Morrison could do more damage to Trump's defense than any witness so far.