The Democrat narrative is that the only conceivable reason to announce an investigation of the Bidens is for Trump's political advantage - that there is no other, independent reason. This begs two equally poignant questions: (1) Why isn't the Biden fact pattern sufficient to justify an inquiry by Ukrainian authorities, and (2) by what logic does one conclude that the mere announcement of an investigation is advantageous to the Trump campaign?
On the second point, if Biden turns out to be the nominee, is there any doubt whatsoever that Trump will fill the airwaves with the particulars of the Bidens' enrichment, positions, conflicts, etc.? By that time (August 2020) who will give a shit about a pathetic, meaningless announcement a year earlier by a foreign leader whose name fewer than ten Americans know? The idea that this announcement constitutes "foreign interference with the American Presidential Election!" is absolutely preposterous. As with the Russian campaign in 2016, one would be hard pressed in 2021 to find a single American voter who even remembers these matters, let alone based their vote on it.
To say that the Democrats' case is flimsier than rice paper does a disservice to rice paper.