I raise this alarm as a loyal liberal who has supported every Democratic candidate for president since I campaigned for Adlai Stevenson in 1952. Yet because of my strong opposition to open-ended criminal laws, some critics on the left have accused me of becoming “President Trump’s attack dog.” Nothing could be further from the truth. I worked to prevent the election of Donald Trump, and since his swearing in, I have been critical of many of his actions, including his travel ban, his rescission of protections for “Dreamers,” his telling the Russians about intelligence gathering and his failure to single out white nationalists for their provocations in Charlottesville.

But elastic criminal laws should not be stretched to cover Mr. Trump’s exercise of his constitutionally authorized power. When the president asked the director of the F.B.I. to drop its investigation into Michael Flynn, the former national security adviser, or fired James Comey from the F.B.I., or provided classified information to the Russians, he was acting within his constitutional powers. Those actions may deserve opprobrium, but they should not be deemed criminal. The proper place to litigate the wisdom of such actions should be at the ballot box, not in the jury box.