Star anchor Megyn Kelly is leaving Fox News for NBC

Megyn Kelly, who arrived at Fox News 12 years ago as a television news neophyte but rose to become one of its two biggest stars, has decided to leave the network to take on a broad new role at NBC News for an undisclosed salary, NBC announced Tuesday afternoon.

The NBC News chairman, Andrew Lack, wooed Kelly away from Fox News by offering her a triple role in which she will host her own daytime news and discussion program, anchor an in-depth Sunday night news show and take regular part in the network's special political programming and other big-event coverage.

The move will herald a seismic shift in the cable news landscape, where Kelly had become the second-most watched host — after Bill O'Reilly of Fox News — and often helped define the national political debate, especially over the last year as Donald Trump regularly attacked her, at times in viciously personal terms.

Kelly's exit will upend Fox News' vaunted prime-time lineup and inject a new dose of tumult just a few months after the departure of the network's powerful founding chairman, Roger Ailes, who was ousted after several women made allegations that he sexually harassed them.

The new deal brings to a close the most anticipated television news contract negotiations since Katie Couric signed with CBS News in 2006, for $15 million a year.

Fox News' parent company, 21st Century Fox, which is controlled by the family of Rupert Murdoch, had offered Kelly more than $20 million a year to stay after her current contract expires this year. Rival networks seeking to hire Kelly away, including NBC News, had made it clear that they could not match that money from Fox, the cable news leader for the last 15 years running.

Kelly's contract is not officially up until the summer, and it was unclear whether Fox News would release her from any contractual commitments that might delay her start at a rival.

In its announcement, NBC said the daytime program would run Monday through Friday at a time to be determined. It is unclear how NBC News would ensure that all of its affiliates would carry it, given that daytime television is often filled with syndicated programs. But people familiar with the discussions said NBC was confident that it would not be a problem. The daytime program would be a mix of news, interviews and panel-like discussions covering a range of issues, not only government and politics.

The Sunday night program, which is yet to be named, would provide Kelly with a continued hand in hard news. And she would be in the mix on NBC News during major political coverage. The network said more details about her role would be announced in the coming months.

A spokeswoman for Kelly, Leslee Dart, did not immediately return a call seeking comment on the deal.

In a statement on Facebook announcing her move to NBC, Kelly thanked Murdoch and his sons, Lachlan and James, along with "the FNC viewers, who have taught me so much about what really matters." She said her time at Fox News "changed my life," but it was time for a new challenge.

"Megyn is an exceptional journalist and news anchor, who has had an extraordinary career," Lack said in a statement. "She's demonstrated tremendous skill and poise, and we're lucky to have her."

In recent months, some of that combat was taking place inside the Fox News headquarters, after Kelly's allegation that Ailes — a mentor and early champion of her career — had sexually harassed her. (Ailes has denied her charges and the others.)

Her allegation was one of several that came to light after another Fox News anchor, Gretchen Carlson, filed a sexual harassment lawsuit against Ailes in July. In a subsequent investigation commissioned by 21st Century Fox, 20 or more women, including Kelly, reported inappropriate behavior by Ailes. But because of her stature at the network and her once close relationship with Ailes, Kelly's account proved instrumental in his ouster.

In her book, Kelly described her decision to step forward as a painful one that came in the face of a networkwide campaign to support Ailes, which she viewed as potentially intimidating to other accusers. Her decision to share her story with investigators drew apparent enmity from some rival stars, with the resentment lingering as she deliberated her next career move.

Most prominent among them was O'Reilly, who said in an interview on CBS News about allegations against Ailes that Kelly shared in her book, "I'm not interested in making my network look bad."

Later that day, he continued the thought in a commentary on his own show in which he appeared to question Kelly's loyalty to Fox by saying, without naming her: "If somebody is paying you a wage, you owe that person or company allegiance. If you don't like what's happening in the workplace, go to human resources or leave."

O'Reilly's contract is also up later this year. The television news and political worlds were closely watching for Kelly's decision as an indication of the network's future in its post-Ailes era. The speculation — and it was just that — went that one or the other would depart and that a decision by Kelly to renew would indicate a shift to a more nuanced ideological sensibility.

Over the years, Kelly, who views herself as more of a news analyst than opinion host, had developed a broader style in the more ideological confines of the Fox News prime-time slate, frequently upsetting expectations for a nighttime Fox personality — for instance, publicly taking on the Republican nominee for president with whom Ailes was friendly (upon leaving Fox, Ailes would go on to serve as an informal adviser to Trump).

James and Lachlan Murdoch, who help run 21st Century Fox, while making clear they want a modern workplace environment at Fox News, have also said the network would not shift away from what Lachlan Murdoch called its "unique and important voice." That voice continues to propel Fox News to the top of the cable news ratings in the nascent Trump era.

Nonetheless, in an interview with the Wall Street Journal in the fall, Rupert Murdoch said money would be no object in keeping Kelly.

People familiar with Kelly's deliberations said she had been entertaining several attractive possibilities, including at CNN and ABC News and in syndicated television.

One person briefed on Kelly's deliberations said that Lack, the NBC News chairman, won over Kelly by starting the talks with a question about what she was seeking, instead of flatly offering possibilities. He then came back with a deal that was tailored to her preferences. A daytime show would give her a schedule that would allow her to see her children off to school and to have dinner with them and her husband, Douglas Brunt, a novelist.