Quid pro quos between countries, when used to serve the national interest, are pretty common place and totally legitimate. As an example, if the US were to give better trade deals and lift sanctions on another country in return for them extraditing a wanted criminal or ceasing material support for insurgents who are harassing their neighbours who are allied to the US.

Trump’s QPQ on the other hand was illegal and immoral because he was withholding military aid that was authorized by Congress for Ukraine in exchange for getting dirt on a political opponent, Joe Biden. Trying to bring down your opponent is a domestic political objective, not a national security one.

The Republican line that ‘Trump was concerned about corruption in Ukraine’ is a farcical line — hasn’t Trump been reducing US government programs into fighting corruption worldwide? If there was a genuine problem with Hunter Biden’s Burisma employment (there wasn’t), why is Trump using his personal lawyer as the envoy rather than going through law enforcement channels?

This was more than a QPQ. It was extortion of a foreign country for personal gain, using money that wasn’t the extorter’s to give.