Andrew Lack touched down at NBC News for a second tour of duty in the Spring of 2015, just as NBC was grappling with a crisis borne out of a false claim Brian Williams made on the company’s flagship “NBC Nightly News.” Now Lack finds himself in another precarious moment.

As the overseer of both NBC News and MSNBC, Lack must quickly hit upon a new direction for NBC’s venerable “Today” show, arguably the linchpin of the news division, now that veteran anchor Matt Lauer has been fired for what NBC called “inappropriate sexual behavior.” And he must do so amid recent scrutiny that has been paid to NBC News in the wake of a decision to allow Ronan Farrow, a recent contributor to “Today,” to take a bombshell report about sexual harassment by movie mogul Harvey Weinstein to the New Yorker after starting it under the aegis of NBC News.

Lack has guided NBC News through tumult in the past. When he was named president of NBC News in 1993, the unit had suffered a black eye in the form of a “Dateline” broadcast in which producers admitted to rigging a pickup truck to catch fire as part of a report on General Motors trucks. GM in turn sued NBC for defamation.

But the Lauer case is a different matter entirely. While it’s not about journalism per se, it has the potential to impugn the news unit’s standing. More allegations are likely to surface, and viewers who watch “Today” – caught unaware Wednesday when anchors Savannah Guthrie and Hoda Kotb announced his termination in the opening moments of the program – are certain to wonder what happened to the news personality who has greeted them for more than two decades each morning on NBC.

NBC News has avoided airing blockbuster stories about famous men harassing women. In the fall of last year, Donald Trump, then a presidential candidate, was caught on a 2005 outtake from NBC’s “Access Hollywood” bragging to correspondent Billy Bush about sexually assaulting and harassing women. As NBC News started to vet the information, it lost control of it.

Someone — the identity of whom has yet to be revealed — sent a copy to the Washington Post, which made it available to the public within hours. NBC News ceded ownership of a major news story, though it was the first to air it on TV. “My gut would have been to put that story on the air” as soon as possible, said Jeff Zucker, president of CNN Worldwide (and the former CEO of NBCU), speaking about the incident a few days after it happened.

And Lack faces the bizarre as well. President Trump in a tweet issued Wednesday morning suggested executives at Comcast and NBC News should be fired for “putting out so much Fake News.” Trump also urged people to “Check out Andy Lack’s past!” Trump hurled invective at MSNBC president Phil Griffin and the cable-news outlet’s morning host Joe Scarborough.

NBC News declined to make executives available for comment.

Lack strikes a colorful figure in the news business – often enthusiastic, always willing to try a new idea that bears no small degree of risk. Brian Williams’ career has rebounded since Lack put him in place in a well-regarded 11 p.m. news hour on MSNBC. It’s Lack who lured former Fox News Channel anchor Megyn Kelly to NBC for a salary reported to be worth $17 million a year and quickly outfitted her with a 9 a.m. morning show that is very different from the third hour of “Today” to which many viewers were accustomed.

It’s also under Lack that MSNBC, often known for its progressively themed primetime programming, has tested out anchors who don’t hew to the network’s template. Greta van Susteren, the former Fox News Channel host, didn’t get satisfactory ratings during less than seven months in MSNBC’s 6 p.m. slot. But Nicolle Wallace, a former communications official in the George W. Bush White House, has thrived since taking over MSNBC’s 4 p.m. hour in April of this year.

Under Lack’s direction, MSNBC’s daytime schedule has dropped the liberal lens on the news and instead become a showcase for NBC News reporting. Hallie Jackson, Katy Tur, Craig Melvin, and others have expanded their profile and the network’s primetime ratings have soared in a post-Trump landscape.

But “Today” is not a cable-news channel that can be tweaked hour by hour. It’s an institution. And Lack, NBC News President Noah Oppenheim and other executives will have to move quickly and decisively to keep that ship moving. When an anchor leaves one of the big broadcast morning programs, it upsets a viewer’s morning routine. Some member of the audience may get a wandering eye, and prove willing to check out Chris Cuomo and Allisyn Camerota on CNN’s “New Day” or Robin Roberts, George Stephanopoulos and Michael Strahan at ABC’s “Good Morning America.”

Lack has long proven eager to hit home runs. But with the viewership for “Today” at stake and questions lingering over why NBC News has seemed reluctant to pursue allegations of sexual harassment , the news executive can’t afford to miss during his next time at bat.