NBC named Chuck Todd the new host of "Meet the Press" on Thursday afternoon, beginning a revamp by network news managers who say they want the iconic program to be the "beating heart of politics."

The announcement confirmed widespread speculation that David Gregory, the moderator of the Sunday morning public affairs program for the past six years, would be replaced by Todd, the NBC News political director.

Not only is Gregory leaving "Meet the Press," he is also leaving the network. His next career move is not yet known.

"The next-generation 'Meet the Press,' led by Chuck Todd, is certain to be the must-watch political destination on Sundays and beyond," NBC News president Deborah Turness said in an internal memorandum that doubled as the network's announcement.

Todd's first day on "Meet the Press" will be September 7. Veteran NBC correspondent and MSNBC anchor Andrea Mitchell will fill in this weekend. In other words, last week was Gregory's last edition of "Meet the Press" -- though the viewers didn't know that at the time.

Gregory confirmed his departure in a series of Twitter messages on Thursday afternoon, hours after CNNMoney reported that the "Meet the Press" moderator change was imminent.

"I leave NBC as I came -- humbled and grateful," he wrote. "I love journalism and serving as moderator of MTP was the highest honor there is."

He added, "I have great respect for my colleagues at NBC News and wish them all well. To the viewers, I say thank you."

Todd, for whom the term "political junkie" seems invented, will remain the political director for the network news division, but will give up his mid-morning MSNBC newscast "The Daily Rundown."

Todd will be the twelfth moderator in "Meet the Press" history. Born on radio in 1945 and reborn for television in 1947, "Meet the Press" is the longest-running show on TV.

Within NBC, it is a cherished brand, but it's also one that has fallen on hard times. With Todd in the anchor chair, NBC hopes to reinvigorate the program and its weekly ratings.

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Turness said, "we have some exciting plans to evolve and update the broadcast under Chuck's leadership that we will be sharing with you shortly."

The announcement about Todd's promotion ends an ugly period of public conjecture about Gregory's fate, made worse by the network's tepid statement of support for him earlier this summer.

When the New York Post's Page Six column said in July that Gregory could be replaced "soon after the November midterm elections," a network representative was quoted as saying, "We heard the same false rumors and suggest you take them with a grain of salt, as we did."

Tepid support, indeed.

Mike Allen of Politico reported earlier this week that Todd was the "likely successor" to Gregory and that the change was "expected to be announced in coming weeks."

That report seemed to accelerate the network's timetable. On Thursday, when NBC's announcement was made, Gregory was in New Hampshire, far from his Washington, D.C., office. Turness, meanwhile, was in New York, having canceled a long-planned trip to London to oversee the "Meet the Press" transition.

Questions about Gregory's future on "Meet the Press" surfaced shortly after Turness took over the news division in the summer of 2013.

She has discussed any number of changes to the program, including, at one point, the possibility of a studio audience. Her memo on Thursday reflected enthusiasm for change.

The best-known "Meet the Press" moderator is Tim Russert, who was appointed to the job in 1991 and died suddenly in June 2008 while preparing for an edition of the program. Under Russert, "Meet the Press" was solidly No. 1 in the ratings race among the broadcast networks.

After Russert's death, Tom Brokaw filled in until December 2008, when Gregory took over. The program now routinely ranks No. 3 behind "Face the Nation" on CBS and "This Week" on ABC.

"This Week" moderator George Stephanopoulos wrote on Twitter after the announcement, "Congrats Chuck Todd. Welcome to Sunday AM fray. Best wishes David Gregory."

And at the end of the day, Todd made his first comments. He wrote on Twitter that he was "honored and humbled to be in the company of great MTP moderators, including David, Tom and of course Tim. All three taught me so much."