WASHINGTON -- The I-word has entered the Washington vocabulary. That forbidden word -- the 11-letter pathway to political damnation, is suddenly, timidly, tiptoeing onto the tongues of capital-dwellers.

A Democrat suggested it on the floor of Congress on Wednesday. A Republican conceded it might be a possibility. And an Independent expressed regret about having to even mention the fear-inducing noun.

Impeachment.

"The president must be impeached," said Democrat Al Green, raising it on the congressional floor Wednesday. "This is not something to be taken lightly. And I do not.... It's a position of conscience for me."

The fact that it's travelled in just one week from the realm of liberal bar-room fantasizing to open discussion in the hallways of Congress indicates the degree of turmoil caused to Trump's presidency in just a few days.

To be sure, impeachment remains a distant hypothetical threat. The more immediate concern for Trump is the mounting pile of investigations, with new elements added Wednesday.

The biggest development was the Justice Department announcing the appointment of a special counsel in the Russia probe. It will led by Robert Mueller, the former FBI director who preceded the now-fired James Comey.

How did this happen? It's been less than two weeks since the president held a victory party on the White House lawn, surrounded by jubilant Republicans, as they celebrated the partial passage of a health-reform bill.

But it turns out a president can accumulate lots of damage by firing an FBI director; changing the story about why; becoming the target of a congressional investigation that's expanding into money-laundering; sharing intelligence with Russia, to the dismay of allies; being accused of interfering with a police probe; chewing out his staff; and seeing enemies within government leak constantly to the press.

Trump fumed about it in a speech to graduates of the Coast Guard Academy.

"Look at the way I've been treated lately, especially by the media," Trump told the ceremony on Wednesday. "No politician in history -- and I say this with great surety -- has been treated worse or more unfairly."

A perceptible shift has occurred. It happened the instant news reports surfaced saying that Comey kept a diary of his interactions with the president and in it the president purportedly asked him to cut short a Russia-related investigation.

That hint of obstruction of justice was a turning point for many -- including Republicans, who are increasingly on Trump's case as the president watches the defensive wall around him begin to crumble.

Three committees, all controlled by Republicans, have requested Comey's records. Two have asked the former FBI director to testify. One has asked for money-laundering records from the U.S. Treasury Department.

A few Republicans have even joined calls for a special prosecutor or independent investigator.

One lawmaker from a ruby-red conservative district, Adam Kinzinger, told CNN: "This has raised real red flags in the level of seriousness. This is about America. It's not about our political parties, or our political future."

Democrats, meanwhile, are using their meagre minority power to push the White House to release transcripts of the Oval Office conversation with Russian officials, and to release any tapes of Comey talking to Trump -- the existence of which the president has hinted at.

They also want to see Comey's memos, as well as the former FBI director himself, testifying before Congress.

Top Senate Democrat Chuck Schumer said it's about preserving America's political institutions: "These requests are reasonable. They're modest. To my colleagues on other side: America needs you. America needs you now. . . . History will judge us."

He's not among those uttering the noun of presidential doom.

Yet others are. A maverick Republican libertarian, Justin Amash, said that if the latest allegations are true, impeachment becomes a possibility. An Independent senator who works with Democrats, Angus King, told CNN when asked about impeachment: "Reluctantly . . . I have to say yes. Simply because obstruction of justice is such a serious offence. And I say it with sadness and reluctance."

The Democratic leadership is discouraging such talk.

No presidential impeachment has reached the two-thirds majority required for conviction in the Senate. In two cases, the Senate acquitted Andrew Johnson and Bill Clinton after they were impeached by the House.

Ousting Trump would require the votes of all Democrats and nearly half the Senate Republicans.

So the party brass intends to start off by whacking Trump with a more modest weapon -- the investigative club and not the nuclear button of impeachment. One Democrat on the intelligence committee said it's important to do the work, build the case against Trump as it comes.

The work must be done diligently, carefully and not be perceived as an effort to nullify the election, said Adam Schiff. Elijah Cummings said he wants to learn what he can, and who knows whether that leads to impeachment.

A New Jersey lawmaker, Joseph Crowley, put it this way: "I'm not afraid of the 'I' word -- it's independent. Independent commission, independent investigator. That's what I support."