In an opinion piece Saturday for the Washington Post, Tribe said Trump's offenses (potential violations of the emoluments clause and interference with FBI's Russian Federation investigation) were piling up and called for the Republican-controlled House of Representatives to launch an impeachment investigation.
Impeachment chatter appears to be heating up among Congressional Democrats - with a second member of the House now explicitly calling for the President to be impeached.
Trump fired Comey on Tuesday, initially arguing that it was based on the recommendation of Deputy Attorney General Rod Rosenstein.
The time has come for Congress to launch an impeachment investigation of President Trump for obstruction of justice.
Rep. Mark Pocan (D-Wis.) said that maybe there should be an "Impeachment Clock" that acts like the famous "Doomsday Clock".
"If the president is, in fact, impeached, then it goes to the Senate...but impeachment is all about having the president charged in the House".
Trump's firing of his Federal Bureau of Investigation director last week has only increased American's concerns about his ability to govern the country.More news: Laptop ban on flights from Europe possible 'within two weeks'
In an appearance Sunday on ABC's This Week, Tribe said the impeachment process is "our system's last resort for someone who treats himself or herself as above the law". The last time I checked, the president of the United States does not forfeit his First Amendment right of free expression upon taking office. Professor Tribe has not alleged that President Trump engaged in treason or bribery.
But Tribe is particularly troubled by Comey's firing and its aftermath.
To say that this does not in itself rise to the level of "obstruction of justice" is to empty that concept of all meaning. "We are facing a constitutional crisis potentially larger and more significant than Richard Nixon's 'Watergate.' As long as Donald Trump remains president, our governing institutions are threatened".
The House has only impeached two presidents before - Andrew Johnson and Bill Clinton. "Impeachment will happen if handful of Republicans in Congress join Dems to put country above party".
Comey's summary firing will not stop the inquiry, yet it represented an obvious effort to interfere with a probe involving national security matters vastly more serious than the "third-rate burglary" that Nixon tried to cover up in Watergate. They claim Trump had pushed for Comey's loyalty.
"It may well produce impeachment proceedings, although we're very far from that possibility".