An important aspect of any criminal charge against a person is whether they showed through their actions that they possessed “mens rea” or an awareness that what they were doing is wrong.
Calling the Ukrainian President with more than a dozen people listening to the call shows that the President had no criminal intent in the call. Asking Zelensky to cooperate with the US Attorney General in the investigations also shows that he was not attempting to do something he understood to be illegal. The benign explanation is that he wanted to be assured that Ukraine was no longer as corrupt as he had heard they were in the past from the examples he was familiar with. He did not want to give aid to a corrupt country.
There is no evidence that anything discussed was about the 2020 election in any way. There is no basis in fact for the Democrats to even bring up this point.
Your words that say President Trump wanted to be asssured that the new President of Ukraine, Zelensky, wanted to end the years of corruption in Ukraine have important merit. I think this was the important reason for the phone call. Trump wanted to take a reading of this newly elected President. I think President Trump has developed a sixth sense about character. I think the investigations into Burisma Holdings and Hunter Biden are happening and being done in a way that there is no interference. Both Hunter and Joe may have some explaining to do. Too bad the wheels of justice take so long.