With his own words over the past two days, President Trump has vastly escalated the stakes and potential consequences of his decision to fire James B. Comey as FBI director, provoking questions about whether his motivations and tactics may have run afoul of the law.

The president also suggested via Twitter that he may have “tapes” of private conversations with Comey, evoking echoes of Watergate and demands by Democrats that he produce what could be critical evidence.

All of that undermines Trump’s credibility as he seeks to name a new FBI director whose independence will be under intense scrutiny and whose most critical job will be to lead the probe into alleged Russian meddling in the 2016 election.

The point of greatest sensitivity raised by Trump’s decision to fire Comey is its potential connection to the former FBI director’s role in investigating what he described as “the nature of any links between individuals associated with the Trump campaign and the Russian government and whether there was any coordination between the campaign and Russia’s efforts.”

In a television interview and on Twitter, the president has given ammunition to arguments by some legal experts that his actions constitute a possible case of obstruction of justice — a central charge in the impeachment proceedings against two presidents in the last 43 years.

(NBC News)

Obstruction is “a very mental-state-based crime,” said Duke University law professor Samuel W. Buell, a former federal prosecutor. “It’s all about the purpose with which it’s done. In theory, trying to intimidate, silence, or even influence someone who is investigating you could be obstruction of justice.”

But whether the unfolding controversy ultimately puts Trump’s presidency at risk is more a question of politics than law.

Given that both houses of Congress are in Republican control, it would take an enormous public outcry for lawmakers to begin the process of attempting to remove the president from office. The same, it appears, probably would have to happen before the Justice Department that reports to him would be compelled to appoint a special prosecutor, much less actually bring charges.

Democrats have escalated the pressure for a more vigorous probe amid statements by Trump that contradict his White House’s initial contentions that Comey’s dismissal was based on the recommendation of Deputy Attorney General Rod J. Rosenstein.

In an interview with NBC News’s Lester Holt on Thursday, the president said: “I was going to fire regardless of recommendation.” He also said that he had pressed Comey during a private dinner to tell him if he was under investigation.

Trump further revealed that the ongoing probe into questions of Russian influence on the 2016 election, which includes a look at the possibility that Moscow was coordinating with the Trump campaign, was one of the factors he considered before firing Comey.

“In fact, when I decided to just do it, I said to myself, I said, ‘You know, this Russia thing with Trump and Russia is a made-up story, it’s an excuse by the Democrats for having lost an election that they should have won,’ ” he said.

(Reuters)

On Friday, the president created another stir with a flurry of tweets, one of which warned that Comey “better hope that there are no ‘tapes’ of our conversations before he starts leaking to the press!”

In an interview with Fox News, Trump declined to say such tapes actually exist, even as congressional Democrats demanded that he produce them.

Sen. Richard J. Durbin (D-Ill.), the second-ranking Democratic senator and a senior member of the Judiciary Committee, said that Trump’s tweet was a “thinly veiled threat” that “could be construed as threatening a witness in this investigation, which is another violation of federal law.”

In an interview, Sen. Richard J. Blumenthal (D-Conn.) added that “there is so much that smacks of obstruction of justice that is swirling around this dismissal and the meetings that preceded it. The exchange that took place with Comey, whichever version you believe, raises very, very serious questions about attempts to pressure an FBI director investigating wrongdoing potentially implicating the president.”

The issue is not Trump’s legal authority to dismiss Comey, which he possesses with or without cause.

“From a constitutional perspective, Trump can make whatever demands of his principal officers he wishes, and can fire them at will,” said Josh Blackman, a law professor at South Texas College of Law Houston.

Comey wrote in a farewell letter to his former colleagues: “I have long believed that a President can fire an FBI Director for any reason, or for no reason at all.”

That decision in Comey’s case, however, becomes legally problematic if it is done with the intent of circumventing an investigation.

“If shown that Trump removed Comey to avoid being investigated? Yes impeachable: abuse of power, corruption, undermines rule of law,” Harvard University law professor Noah Feldman tweeted Friday.

The questions about Trump’s motives are being fueled, increasingly, by his own words in interviews and on Twitter.

“The fact that Trump is saying these things in the midst of all of this is proof positive that he is not listening to counsel — in fact, he may not even be talking to counsel,” Buell said.

Then again, he added, the many contradictory statements by Trump and top officials may have served to “muddy the waters” enough that it is impossible to determine his actual intent.

Whether all of this could jeopardize the survival of Trump’s presidency is another question, and one whose answer is much farther down the road.

The Constitution specifies that the president can be removed only for treason, bribery, or “other high Crimes and Misdemeanors,” the definition of which it leaves to Congress.

Obstruction of justice, however, was deemed to be one of the infractions meriting impeachment proceedings both in the case of Richard M. Nixon in 1974 and of Bill Clinton in 1998.

Nixon, having lost the support of his own party, resigned after the House Judiciary Committee passed three articles of impeachment in connection with the Watergate scandal; Clinton remained in office after being acquitted by the Senate in articles that stemmed from his alleged efforts to cover up an extramarital affair with White House intern Monica Lewinsky.

Thus far, only a handful of the more strident Democrats have engaged the possibility of impeachment in Trump’s case.

The better strategy at this point, party leaders have decided, is to pepper Rosenstein and others at the Justice Department with letters of inquiry, call for hearings and pressure Republicans to get on board with a more aggressive investigation.

Asked if he thinks that the controversy could be leading to impeachment proceedings, Blumenthal said: “Prejudging the results of any inquiry now is premature. Right now, the important point is to follow the evidence, to pursue every investigative lead and every potential witness diligently and promptly, and — I just might add this point — providing the resources that are needed.”

Democrats are also coalescing in their demand for the Justice Department to appoint a special prosecutor — something they are certain to press when Rosenstein visits Capitol Hill to brief the full Senate next week.

With Trump’s approval ratings already at record lows for a president at this early point in his term, public opinion will be an important factor. Republicans are already bracing for a difficult midterm election next year — and some fear that their control of the House may be at risk.

In the end, public perceptions may matter more than the letter of the law in determining if and how Trump weathers the most severe storm to hit his turbulent young presidency.

“This remains, I think, a political problem only,” Blackman, the law professor, said. “What will take Trump down is not the Constitution, but public opinion polling and the ballot box.”

Robert Barnes, Ed O’Keefe and Elise Viebeck contributed to this report.