Sen. Chris Murphy (D-Conn.) argued on CNN's "State of the Union" on Sunday that Ukrainian officials will not say that President Trump conditioned military aid on their announcement of political investigations because "they are presently reliant on the goodwill of Donald Trump."

"Now, the Ukrainians are always going to try to put a good spin on this. The Ukrainians aren't going to come out and accuse the president of extortion. Why? Because they are presently reliant on the goodwill of Donald Trump in order to keep that country safe. They can't take on the president because at any moment he could stop the security aid once more. So nobody should be surprised when the Ukrainians are trying to put as good a spin on this as possible, are trying to stay in the president's good graces. Because right now the president still holds enormous leverage over that country's independence and sovereignty."

The big picture: Top Ukrainian officials, including the country's foreign minister as recently as Thursday, have denied that the Trump administration explicitly linked the aid to an investigation into former Vice President Joe Biden and his son. Ukrainian President Volodymyr Zelensky has said that he did not feel pressure and that he does not want to interfere in "democratic, open elections" in the U.S.

On the U.S. side, however, EU Ambassador Gordon Sondland has testified that he told a Ukrainian official that the country would likely not receive the aid unless it caved to Trump's demands.

Past reports also indicate that the Ukrainian government felt pressure from the Trump administration.

Top Ukraine diplomat Bill Taylor testified last week that it would be viewed as a sign of weakness for Zelensky to acknowledge to Ukrainians that he capitulated to a foreign leader.

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