Friends have tried over the years to convince Lisa Monaco, President Biden’s nominee to become the No. 2 Justice Department official, to get a Twitter account. She should offer her national security expertise not just at conferences, they’d argue, but on social media.

“Nope, boring is my brand,” she liked to joke, according to colleagues. After years in some of the most demanding national security jobs in government, Monaco, 53, whom former president Barack Obama used to call “Dr. Doom,” is due to appear Tuesday for her Senate confirmation hearing to become the next deputy attorney general.

Monaco’s ties to Biden go back to the 1990s, when she was a junior staffer on the Senate Judiciary Committee he led. From there, she went to law school and became a federal prosecutor, rising quickly in the Justice Department and eventually joining the team that prosecuted Enron executives over that firm’s self-destructive financial trickery. That group of lawyers would later hold some of the most important posts inside the agency.

Andrew Weissmann, a former prosecutor who was part of the Enron team, said Monaco has always shown “the same rigorous and dispassionate examination of the law and facts, unafraid of making the tough calls necessary to serve the public interest.” She was, he said, “the truly ideal choice” to become deputy attorney general, a job law enforcement professionals call “the DAG.”

Historically, the DAG is a critical but low-profile position — a kind of bureaucratic traffic cop overseeing the FBI, the Drug Enforcement Administration, the Marshals Service, the Bureau of Prisons and the Bureau of Alcohol, Tobacco, Firearms and Explosives. Often, the deputy attorney general tackles the problems and disagreements that cannot be solved by lower-level officials.

In recent years, however, the job has been anything but low profile. The Trump administration’s first deputy attorney general, Rod J. Rosenstein, oversaw Robert S. Mueller III’s special counsel investigation into Russian interference in the 2016 election and the Trump campaign, and he frequently faced the fury of President Donald Trump and Republican lawmakers for various developments in that case. His successor, Jeffrey Rosen, was running the Justice Department in January of this year when Trump supporters launched a short-lived insurrection at the U.S. Capitol, in what many current and former government officials consider a major security and intelligence failure.

If confirmed, Monaco would be second-in-command to Merrick Garland, whose nomination to be attorney general is scheduled to be voted on by the full Senate in coming days. Biden has said Garland, Monaco and the rest of his Justice Department picks are tasked with restoring the Justice Department’s independence from partisan politics and adherence to the rule of law after the Trump years, when the president regularly demanded the department investigate his political opponents and exonerate his friends and allies.

In interviews during Trump’s presidency, Monaco often voiced frustration that career government officials and technical experts were disregarded or dismissed for political reasons.

“As concerned as I am about some of the policy decisions, the thing I worry about over the long term is the damage to institutions, the damage to appreciation of expertise and making the word ‘career official’ or ‘career public servant’ into somehow a dirty set of words,” she said on a podcast in 2017. “ . . . I worry that there seems to have taken hold in Washington a sense that those people aren’t worth listening to, and that they don’t provide value, and there’s a rejection of that. And I think that’s unfortunate and really dangerous.”

Through a Justice Department spokesman, Monaco declined to comment for this report.

Monaco has a résumé full of the kind of government jobs that come with long hours, tough decisions and public second-guessing. During the Obama administration, she worked as the head of the Justice Department’s national security division, among other roles. Obama considered nominating her to be the FBI director, though he ultimately chose James B. Comey. Monaco served instead as Obama’s homeland security adviser, often as the White House point person on major disasters and tragedies, such as the 2016 shooting at the Pulse nightclub in Orlando.

Because Monaco was often the one to bring word of such horrible events, Obama jokingly called her “Dr. Doom.” But he came to rely on her so extensively that he also put her in charge of the government’s response to an Ebola outbreak in West Africa in 2014 — a move some officials privately questioned, since it seemed to stretch the definition of national security.

“I don’t know anybody in government, or outside government, who is more responsible, rigorous, and thoughtful about how they do their job and how they serve the public,” said Preet Bharara, who worked with Monaco extensively when he was the U.S. attorney in Manhattan during Obama’s presidency.

Bharara said Monaco has “spent her whole life in public service, and has always answered the call, no matter what. She’s not at all about politics, she’s about getting the job done in a legal and pragmatic way.”

Monaco’s nomination is not expected to generate much resistance from Senate Republicans, particularly given the format of Tuesday’s hearings, where she will be questioned at the same time as Vanita Gupta, Biden’s nominee to the No. 3 position at Justice.

Gupta, a civil rights advocate and a Justice Department veteran, is likely to draw much more attention from lawmakers at the hearing, as some Republicans have signaled unhappiness with her nomination and both parties seek to make points on politically loaded issues of voting, policing and minority rights.