Senior White House correspondent Jake Tapper is leaving ABC News for CNN.

Tapper will anchor a weekday program on CNN. TVNewser hears it will be the 4pmET hour, currently filled by “The Situation Room with Wolf Blitzer.” He will also serve as the network’s chief Washington correspondent.

Tapper’s departure, which has been speculated about since earlier this year, was announced by ABC News president Ben Sherwood in a memo to staffers this afternoon. “A ferocious reporter – and now a best-selling author – he has built a reputation as one of the most prolific and multi-talented journalists on the beat, scoring scoop after scoop,” Sherwood wrote.

Sherwood also announced the promotions of Jonathan Karl and Martha Raddatz at ABC. Karl will move from Capitol Hill to the White House, stepping into Tapper’s role, becoming chief White House correspondent.

Raddatz has been named ABC’s chief global affairs correspondent (not to be confused with Christiane Amanpour, who is ABC’s global affairs anchor). She will also become the primary substitute for George Stephanopoulos on “This Week,” and will be a regular contributor to the program’s roundtable.

This is CNN’s second major talent poach from ABC News this year. John Berman, who anchors “Early Start” on CNN, joined ABC in May. CNN’s senior vice president of talent, Amy Entelis, spent more than 30 years at ABC News.

The full memo from Sherwood, as well as CNN’s release, is after the jump.

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