A mere four days ago -- an eon in Trump time -- the president issued a not-so-veiled threat to James Comey, the man he had recently fired as FBI director.

Bad move, Mr. President. Bad move.

Comey has now called Trump's bluff, trumping the threat of presidential tapes that probably don't exist with written memos that probably do exist. According to Comey associates, the longtime prosecutor wrote and kept long, detailed memos immediately after each of his encounters with the president. One of those memos allegedly documents Trump's effort in February to end the FBI's criminal and counter-intelligence investigation into Lt. Gen. Mike Flynn, a close Trump associate who had just resigned as national security adviser.

According to that memo, Trump cleared the room after a high-level White House meeting on Feb. 14 and ordered Comey to remain, so that they could have a private conversation. “I hope you can see your way clear to letting this go, to letting Flynn go,” Trump then told Comey, according to the memo. “He is a good guy. I hope you can let this go.”

No, it's not a direct order to end the investigation, but it is at very least a strongly worded suggestion. And a presidential "suggestion" carries an awful lot of weight, particularly to an underling who had already been given cause to think that his job was on the line. A president simply cannot try to interfere in the course of a law-enforcement investigation into one of his friends, especially when that investigation had -- and has --  at least the potential to implicate the president himself.

Imagine, for example, a private conversation a year ago between Barack Obama and Comey, in which Obama tells Comey that “I hope you can see your way clear to letting this go, to letting Hillary go.” Imagine that Comey ignored the suggestion, and was later fired by Obama.

Imagine the uproar that would have erupted, and compare it to what you're seeing now.

Already, people who would never question the veracity of an FBI agent's interview notes over the claims of a suspect with a reputation for lying are doing that exact thing. "Just because you write it down, it doesn't mean it's true," as Brian Kilmeade put it on Fox & Friends this morning.

And if Comey indeed has a collection of such detailed memos, one of them probably includes an account of the January dinner at which Trump allegedly demanded personal loyalty from Comey as the price of keeping his job. They may also contain other bombshells that we have yet to imagine.

Even Republicans in Congress are beginning to understand the size and scale of this. Sen. John McCain is openly comparing it to Watergate. The carp-like Jason Chaffetz, who until now has been willing to swallow anything that Trump fed him, has roused himself as chair of the House Oversight Committee to demand that the Justice Department turn over all of Comey's memos.

As a result, Comey himself will almost certainly testify, in public and under oath. Congress will want access to others in the White House who may be able to corroborate some portions of his memo. For example, Jared Kushner and other top Trump associates were allegedly among those cleared from the meeting room by Trump so he could speak with Comey privately. Their testimony may be needed to confirm those actions, and perhaps to explain what Trump wanted to discuss with Comey that even his closest confidantes could not be allowed to hear. Furthermore, if tapes really do exist of such conversations, they are now extremely relevant and will have to be produced.

Blood is in the water. When even the carp start circling, blood is in the water.