Alan Dershowitz has a piece up at the Gatestone Institute website pointing out some issues with the prosecution of Senator Menendez:
Senators should not have to fear that the Executive Branch will unleash prosecutors to go after politicians who are critical of the administration. Equally dangerous are prosecutors who seek to curry favor with the administration by prosecuting its enemies without even being told to do so.
To protect against unchecked power by the executive, the framers included the "speech or debate" clause in our Constitution, protecting Members of Congress from being prosecuted for exercising their legislative power, including oversight. These protections are fundamental to our system of checks and balances. A questionable prosecution against a disfavored legislator, based on campaign contributions from an old friend followed by actions that might benefit that friend, threatens this balance of power.
That is why all Americans, regardless of party affiliation, must be concerned about the criminalization of policy differences and the excessive discretion vested in those who prosecute elected officials.