If Joe Biden's so dirty, why haven't we heard about it? I find it hard to believe that the Republicans couldn't turn up a whole lot more of whatever dirt there is... The only thing we've heard over and over again is how Biden pressured Ukraine to fire its [corrupt and ineffective] anti-corruption prosecutor at the behest of the US government and with the full support of most of Western Europe after said prosecutor had finished investigating Burisma for conduct that occurred before Biden's son joined the board. If you twist the timelines and omit some of the relevant details, it sounds like maybe there could be something there, but look closely and that whole "case" falls apart...
There are legitimate ways to investigate alleged wrong doings, many of them at Trump's legitimate disposal. Did he make use of them? No -- Also, note that the pressure was for "a public announcement," not for an actual investigation. Trump's notoriously sloppy (slippery?) about semantics, but this distinction was not a one-time slip.
That said - What does Biden's possible corruption have to do with Trump's abuses? Nothing. And what would Biden know about Trump's conduct? Again, nothing. The only purpose of Biden's potential testimony would be to distract from Trump's conduct and lend credibility to his accusations.
"If Joe Biden's so dirty..." How does organized crime work? Think Mafia structure. Think The Godfather. The corrupt families operate right out in the open. How? They have control over: cops, police chiefs, accountants, lawyers, judges, politicians, media. Nobody rats on the Mafia. They function with impunity to the detriment of law-abiding citizens and businesses and the legitimate criminal and media establishments. Speak up and you get blackballed from your career or worse.
"There are legitimate ways to investigate..." Oh, yes, there are. Just stay tuned for AG Durham's indictments!
"What does Biden's corruption have to do with Trump's abuses?" It all boils down to this: Was Trump "digging up dirt on a political rival" (D claim of abuse) or "asking for help in a criminal investigation that involved the Biden family" (R claim of no abuse)?
In order to assess if R claim is legitimate, you need to be able to provide evidence and testimony of people who can attest to the fact that there were crimes, how those crimes were being covered up, and how Trump was investigating those crimes. For the D's to say that the Biden family is irrelevant is equivalent to the D's saying that any crimes or investigation were irrelevant, which then supports the idea that this was merely an abuse of Trump's power for political reasons.
By international treaty, Trump was within the law to ask Ukraine to help out the US in a criminal investigation, regardless of who was at the center of the investigation. (Biden was not even a candidate at that time.) Trump asked for evidence "for us" (the American people) in a criminal investigation. After all, it is the US taxpayers from whom the billions of dollars have been stolen. There should not be a differentiation between people who are politicians and non-politicians when it comes to application of our laws. Being a political candidate should not shield anyone or anyone's family.
If you think delaying aid was a crime, it is within current practice to ensure the money is going to be used 'correctly' first.
If you think delaying aid was abuse of power, see above.
If you think delaying aid was a coercive tactic, see transcript and Ukraine's President's own statement of no pressure.
The D's don't want any focus put on the Biden family's crimes. They want you to think that this was all for Trump's personal political gain. Can it not be argued that this entire protracted impeachment is a D tactic for their own political gain? Why the 33 day delay to get the articles to the Senate? The needless blathering on for days regurgitating the D's weak case? The unceasing MSM badmouthing of Trump less than 10 months before Election Day 2020? Oh, no, none of that could be for political purposes, could it? Is that abuse of power?