On Jan. 20, 2017, Donald Trump swore to “faithfully execute the office of president of the United States … [and] preserve, protect and defend the Constitution of the United States.”

Presidency scholars will admit readily that this oath is full of ambiguity and that many of our past presidents crossed constitutional boundaries and engaged in morally untenable behavior, such as lying, scapegoating and staging cover-ups.

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Abraham Lincoln

suspended

the writ of habeas corpus. Franklin Roosevelt signed an

executive order

that led to the internment of more than 112,000 Japanese-Americans. And since Harry Truman sent troops into North Korea, as Lou Fisher with the Center for the Study of Statesmanship at the Catholic University of America

showed, “

Presidents have exceeded constitutional and statutory authority in exercising the war power

.”

From Crédit Mobilier and Teapot Dome to Watergate and the Lewinsky affair, plenty of scandals have swamped previous administrations and left a lasting stain on presidents.

Still, no president has come close to President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE and the volume and scope of his behavior.

Last October, Harvard law professor and Hoover Institution senior fellow Jack Goldsmith described Trump as “a Frankenstein's monster of past presidents’ worst attributes: Andrew Jackson’s rage; Millard Fillmore’s bigotry; James Buchanan’s incompetence and spite; Theodore Roosevelt’s self-aggrandizement; Richard Nixon’s paranoia, insecurity and indifference to law; and Bill Clinton William (Bill) Jefferson ClintonAnxious Democrats amp up pressure for vote on COVID-19 aid Barr's Russia investigator has put some focus on Clinton Foundation: report Epstein podcast host says he affiliated with elites from 'both sides of the aisle' MORE’s lack of self-control and reflexive dishonesty.”

It’s appropriate to add Warren Harding’s superficiality and lack of a moral compass.

Trump did not take an oath to protect himself at all costs. But neither he nor his ardent supporters are wont to admit this. They say it’s a “witch hunt,” or only campaign finance.

Yet, despite having only limited information about special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s investigation, the long arm of the law looks like a gigantic octopus at the moment.

With tentacles running in every direction, all parts of the Trump brand — his presidency, his business, his foundation and his family — are imperiled. If Trump had one iota of sense, he’d resign (via Twitter?). Then again, since many of his legal troubles in New York would persist even if a newly-installed President Mike Pence Michael (Mike) Richard PencePence vows for law and order everywhere Trump met with chants of protest as he pays respects to Ruth Bader Ginsburg The Hill's 12:30 Report: Ginsburg lies in repose MORE were to grant him a pardon, he may perceive the Oval Office's Resolute Desk as the far better perch from which to defend himself.

In addition to obtaining a guilty plea from Trump’s personal attorney, Michael Cohen, the prosecutors working for the U.S. Attorney’s Office in the Southern District of New York have made immunity agreements with David Pecker, publisher of the National Enquirer, and Allen Weisselberg, chief financial officer of the Trump Organization. In a possible violation of federal campaign finance law, money was given to Stephanie Clifford and Karen McDougal to keep stories about their alleged extramarital affairs with Trump out of the news prior to the 2016 election.

Cohen’s plea is only one small piece of the legal puzzle Trump faces. First, along with suing the Trump Foundation, the attorney general for the State of New York has notified the IRS and the Federal Election Commission about additional possible campaign finance violations. Second, Cohen was subpoenaed by the New York Tax Department for information related to the foundation. Third, the Manhattan District Attorney is looking into criminal charges.

Another lawsuit against the Trump Organization is in the U.S. District Court for Maryland; it alleges that the president violated the emoluments clause of the Constitution because he remains involved in his business. While the Justice Department has filed an appeal, attempting to stop the lawsuit from moving forward, there is a question about the legality and profitability of the Trump hotel in Washington.

Then, of course, there is the Mueller investigation into meddling by Russia in the 2016 election and the possible collusion of Trump and his campaign. Prosecutors have secured guilty pleas from Michael Flynn, former Trump national security adviser, and George PapadopoulosGeorge Demetrios PapadopoulosTale of two FBI cases: Clinton got warned, Trump got investigated Trump says he would consider pardons for those implicated in Mueller investigation New FBI document confirms the Trump campaign was investigated without justification MORE, a former Trump campaign adviser, for lying about their Russian contacts, and have indicted 13 Russian nationals, 12 Russian military intelligence officers, and three Russian companies. And there are more who have been charged or pleaded guilty.

Trump’s former campaign chairman, Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE, was convicted last week on eight counts of tax and bank fraud. His next trial for unregistered lobbying for foreign interests is scheduled in mid-September in Washington.

Still more questions surround many of Trump’s former advisers, including Roger Stone Roger Jason StoneThe agony of justice Our Constitution is under attack by Attorney General William Barr Justice IG investigating Stone sentencing: report MORE and Donald Trump, Jr. There can’t be this much smoke without a fire, one might think.

And none of what is detailed above even takes in the thousands of Trump’s lies, which have potential to irreparably damage the institution of the presidency.

Congress always should broach the prospect of a presidential impeachment with caution and circumspection, and much about this investigation remains a mystery. Yet, Republicans might ask themselves one question before the election (because waiting until after it will look even more craven than it does now): If the totality of Trump’s not just alleged wrongdoing but also his actions in the face of these inquiries don’t rise to “high crimes and misdemeanors,” would anything — ever?

Lara M. Brown, Ph.D., is an associate professor and director of the Graduate School of Political Management at the George Washington University, and formerly was an assistant professor of political science at Villanova University. She frequently appears on TV and radio programs as an expert on American political history, party development and national elections. Follow her on Twitter @LaraMBrownPhD.