Hailing her longtime role as a “trusted adviser,” President Barack Obama formally named U.N. Ambassador Susan Rice as his next national security adviser on Wednesday.

Obama tapped Rice, a target of Republican criticism in recent months, to succeed Tom Donilon; the president also nominated Samantha Power, a longtime foreign policy adviser, to take over Rice’s role at the United Nations.

“I am absolutely thrilled that she'll be back at my side leading my national security team in my second term,” Obama said of Rice, a longtime confidant whose role in publicly explaining the administration’s initial assessment of last year’s terror attack in Benghazi, Libya, has made her a lightning rod for criticism.

Charles Dharapak / AP President Barack Obama stands with U.N. Ambassador Susan Rice, his choice to be his next national security adviser, right, current national security adviser Tom Donilon, who is resigning, second from right, and Samantha Power, his nominee to be the next UN Ambassador, left, Wednesday, June 5, 2013, at the White House.

“I'm deeply honored and humbled to serve our country as your national security adviser,” Rice said at a White House event to formally announce the shake-up, just the latest instance of staff turnover on Obama’s foreign policy and national security teams in his second term.

Rice also told Obama she was “deeply grateful for [his] enduring confidence,” a seeming nod toward the whirlwind of controversy around her role in the Benghazi explanation, which helped scuttle her chances of becoming secretary of State.

Republicans who targeted Rice over the handling of the 2012 attacks in Benghazi reacted with the knowledge they have no role in confirming her for the post. “Obviously I disagree [with Obama’s] appointment of Susan Rice as Nat'l Security Adviser, but I'll make every effort to work [with] her on [important] issues,” Arizona Republican Sen. John McCain, one of Rice’s foremost critics on Benghazi, wrote on Twitter.

Sen. Rand Paul, a Kentucky Republican with designs on seeking his party's presidential nomination in 2016, was sharply more critical.

"I can’t imagine that we would be keeping Ambassador Rice in any significant position, much less promoting her to an important position," he said on Fox News.

Power is not without controversy, either. She stepped down from the Obama campaign after referring to Hillary Clinton, then Obama’s opponent in the Democratic primary, as a “monster.”

But her nomination might not be held up by concerns about Rice and Benghazi.

"I support President Obama's nomination of Samantha Power to become the next U.S. Ambassador to the United Nations," McCain said in a separate statement. "I believe she is well-qualified for this important position and hope the Senate will move forward on her nomination as soon as possible."

NBC News' Chuck Todd joins Morning Joe to report on the breaking news that Susan Rice has been tapped by President Obama to replace Tom Donilon as National Security Adviser.

Republicans have vocally criticized Rice for emerging on the Sunday morning talk show circuit on the weekend following the Benghazi attack, where she asserted that the attacks were the spontaneous outgrowth of protests related to an anti-Islamic video. In the months since then, senior Republicans have demanded more information about how the talking points provided to Rice were drafted; many in the GOP have suggested the talking points were motivated by electoral politics, since the attack occurred during the height of last fall’s presidential campaign.

The furor was enough to prompt Rice to withdraw her name from consideration to become Obama’s next secretary of state earlier this year.

Had the president nominated Rice to become secretary of state, she would have been forced to undergo bruising confirmation hearings; her new appointment as national security adviser does not require Senate confirmation. She complained about the “very prolonged, very politicized, very distracting and very disruptive” process of confirmation hearings.

Last month, Vice President Joe Biden praised Rice and her role in the Obama administration, saying she had "the absolute, total, complete confidence of the president."

NBC News' Chuck Todd, Alastair Jamieson and Ian Johnston contributed to this report.

This story was originally published on