Thx to Mr. Dershowitz, Senate Republicans are fundamentally misinformed about what grounds for impeachment the Constitution allows. Abuses of power ARE AT THE CORE of impeachable conduct, whether or not they constitute crimes. /1
No federal criminal laws EVEN EXISTED when the impeachment clause was adopted. Arguing that impeachment requires a violation of a non-existent body of laws is nonsensical. As Hamilton explained, impeachment was created for "the abuse or violation of some public trust."/2
SCOTUS made clear that impeachment is a vital safeguard against presidential “misconduct” or “abuses of office.” Even House Rs’ witness agrees a pres. “can be impeached for a noncriminal act.” And even AG Barr has written non-criminal "abuses of discretion" are impeachable. /3
Multiple impeachment proceedings have not involved allegations of crimes. Even the allegations against Nixon were grounded in a “serious violation of [his] constitutional obligations as President, and not the fact that violations of federal criminal statutes occurred.” /4
Senate Rs are being told to accept a constitutionally dangerous argument: that the Pres. can commit any abuse of power to pursue any personal ends he desires with impunity, and Congress cannot hold him accountable. That's not a President. That's a King. /5
Until Trump was caught red-handed, there really was no dispute that abuses of power are impeachable. Here’s more background: leahy.senate.gov/download/presi… 
