What changed Trump's mind on $400 million in Ukraine aid?

Portman’s call was part of a broader congressional campaign to push Trump to lift the hold on the aid. Vice President Mike Pence — who was in the room with Trump when he spoke to Portman — had just returned from a meeting in Poland with Ukraine’s new president and was urging Trump to release the money.

The President and his top officials were also becoming aware of concerns inside the administration that freezing the funds was improper and could possibly lead to much bigger problems…

On September 9, two days before the call with Portman, Gordon Sondland, the ambassador to the European Union, told Trump that concerns were being raised that the President’s actions amounted to a quid pro quo.

Around the same time, White House lawyers informed top officials in the West Wing that a member of the intelligence community had filed a formal whistleblower complaint about Trump’s Ukraine dealings.