It could happen.

President Pelosi? It could happen.

Robert Atkins and Adam P. Frankel

What happens when a Democratic speaker of the House - third in line to the presidency, according to the Presidential Succession Act of 1947 - is suddenly thrust into the Oval Office, succeeding a Republican president and vice president who resign, embroiled in scandal?

Such a scenario is attracting attention - #PresidentPelosi was trending on social media after last week's announcement of an impeachment inquiry - even though it may seem far-fetched that President Donald Trump and Vice President Mike Pence would be forced from office over abuse of power related to the administration's dealings with Ukraine or other misdeeds.

This was a more urgent question in the fall of 1973. On Oct. 10, Vice President Spiro Agnew resigned, pleading nolo contendere to charges of tax evasion. Ten days later, President Richard Nixon ordered the firing of Watergate special prosecutor Archibald Cox in what is widely known as the Saturday Night Massacre. As hearings began in the Senate and the House on the nomination of Agnew's successor, Gerald Ford, questions swirled about the possibility that Democratic House Speaker Carl Albert, D-Okla., might assume the presidency.

So real was the possibility that Ted Sorensen, a speechwriter and close adviser to President John F. Kennedy, wrote a secret 19-page memorandum to Albert, offering recommendations for what to do and what to say in the event that Nixon resigned before Ford could be confirmed and Albert suddenly found himself sitting in the Oval Office. Although long forgotten, the memo is timely in this chaotic political moment, when a Pelosi presidency, however improbable, is not impossible. It reminds us that our faith in representative self-governance may yet be salvaged.

With the country facing uncharted territory - the only impeachment in American history had come more than a century before - Sorensen, who knew and liked Albert from White House breakfasts with congressional leaders during the Kennedy administration, wrote to the speaker nine days after the Saturday Night Massacre to alert him that "whether you wish it or not, you could become President at any time."

Nixon's "sudden resignation . . . will always be a possibility," he wrote, advising Albert to devote serious consideration (albeit silently) to a potential presidency.

Albert agreed, asking Sorensen, then a lawyer in private practice, to send him "a rough draft" of a contingency plan. Sorensen was no stranger to presidential transitions. He helped President-elect Kennedy staff the New Frontier in 1961 and endured the abrupt transition in 1963 after Kennedy's assassination. For decades after leaving the White House, Sorensen would be called upon to offer guidance to presidential hopefuls looking for a strong start should they capture the White House.

But the memo Sorensen wrote to Albert on Nov. 8, 1973, was unlike any other he had drafted - and one he could not have foreseen would resonate more than 45 years later. Sorensen was acutely aware of the potential political fallout if word of the memo got out, and he urged Albert to keep its existence a secret. "If discovered," Sorensen noted, the memo "might be misinterpreted as evidence of an improper motivation on your part for the President's ouster." Such delicate sensibilities seem long gone and unlikely to return in a world where political motives are almost assumed.

To help inoculate the speaker against such charges, Sorensen advised Albert to state unequivocally upon entering the Oval Office, "I shall not be a candidate for the presidency in 1976 or at any other time." He also advised Albert to commit to building "a nonpartisan administration of national reconciliation and unity" filled with "the best men and women in the country available for the job, regardless of party."

Sorensen preemptively raised a question he knew a President Albert would probably face: Should Albert, a Democrat, step aside in favor of a Republican vice president once he was confirmed? No, Sorensen argued. "That would only heighten the impression of political instability in our government. You are the legitimately chosen successor selected by our most representative body under a long-standing plan adopted by the Legislative Branch." This faith in the lawful and orderly transition of power is one we ought to remember as the country confronts a commander in chief who may be unwilling to step aside, even after a defeat at the polls.

Most of the memo, however, contained practical recommendations for what to do on Day One and those immediately following it - nuts-and-bolts concerns such as where and when Albert should take the oath of office. Perhaps ironically for a speechwriter, Sorensen cautioned against a full-scale inaugural address, arguing instead for a short speech emphasizing Albert's claim to office and themes of national unity.

Among the top priorities Sorensen recommended for an Albert administration was preserving Nixon's files for review by the appropriate authorities. That advice pertains today, perhaps more so. Watergate was confined largely to conversations in the West Wing, but the perfidy, corruption and possible criminality of the Trump administration extend across the executive branch and the globe. Finding the files, documents and transcripts this White House has withheld from Congress and reportedly "locked down" will require a full-time team of forensic experts and investigators if all the damage done is to be uncovered and remedied.

Remembering the crucial and largely successful efforts to project calm, strength and stability following Lyndon Johnson's ascension after Kennedy's death, Sorensen urged Albert to demonstrate to the government, the public and the world that he was on top of things by delivering an address to a joint session of Congress in his first week in office, as Johnson had to acclaim in 1963.

Some of Sorensen's guidance would be out of place today: His recommendations on personnel, for example, reflect the needs of a smaller White House staff than exists in 2019. His advice on managing the press - urging Albert to hold a news conference and limit other public statements - does not account for the demands of today's voracious media environment. One list of "wise men" to consult includes no women or people of color, a glaring omission for Sorensen, an early champion of civil rights, and something as unwise today as it was then.

And yet, Sorensen's memo will be an essential - if not the only - guidebook for House Speaker Nancy Pelosi, D-Calif., should she find herself getting closer to the Oval Office. The vice president appears to be a witness, at least, to the affairs under investigation, so the prospect of the House speaker's ascension is not as remote as it seemed just a week ago. If Sorensen's advice sounds somewhat quaint, it is only because we have drifted so far off the course set by previous presidents and the Founding Fathers.

No matter who succeeds this president, or when, the Sorensen memo is a road map to restoring the dignity, integrity and basic function of the nation's highest office. The chaos created by the current occupant's heedless, indulgent and volatile leadership - if it can be considered "leadership" - calls for attention to the national interest and preparation to avoid the kinds of hasty, unwise judgments and actions that can result in catastrophic mistakes. Although from another time, the Sorensen memo offers sage counsel for undertaking such preparations and a plan to steady our careening country and get it back on track.