You can disagree with Alan Dershowitz on minutiae, but you CANNOT reasonably dismiss his general argument. For example he downplays Biden’s misdeeds saying, basically oh, no, you can’t impeach here because there must be crimes like bribery involved. Well, the whole thing is about bribery.
He then reasonably argues that you can’t impeach a president for crimes that occurred before he was president. This is true, unless there was a coverup orchestrated by his administration to cover crimes, using federal agencies. That’s a criminal conspiracy. The bonus: if you conspire to hide criminal activity, EVEN IF THAT ACTIVITY HAS SURVIVED THE STATUTES OF LIMITATIONS, the underling crime can be resurrected and prosecuted.
All that said, Dershorwitz has a clear-headed argument on recusal and prosecutorial nonsense. His entire career has been built on doing the right thing even if it wasn’t popular or went against the Dem tribe, of whom he is a member. We could all take a lesson.