President Barack Obama formally introduced Denis McDonough as his chief of staff on Friday, describing his deputy national security adviser as not only a straight-shooter, but also a close friend.

Obama debuted McDonough, whom the president had been widely expected to select, at the White House, saying he had been "counting on Denis for nearly a decade."

McDonough, a longtime adviser to Obama who has advised the president largely on matters of national security, succeeds outgoing chief of staff Jack Lew. The president has nominated Lew to become the next secretary of the treasury.

"He's the consummate public servant who plays it straight," the president said. "And that's the kind of teamwork that I want in the White House."

Of McDonough's national security advice, Obama said: "Denis has played a key role in every major national security decision in my presidency."

McDonough's ascension coincides with a broader staff overhaul at the White House. Among the changes included elevating White House communications director Dan Pfeiffer to a senior adviser role; Jennifer Palmieri, Pfieffer's deputy, takes over that role. Rob Nabors, the director of legislative affairs, was promoted to a deputy chief of staff position. Miguel Rodriguez takes over that role.

Carolyn Kaster / AP

President Barack Obama, with current White House Chief of Staff Jack Lew, right, announces that he will name current Deputy National Security Adviser Denis McDonough,left, as his next chief of staff, Friday, Jan. 25, 2013, in the East Room of the White House in Washington.

Obama also singled out his longtime political adviser, David Plouffe, whose last day at the White House is on Friday, for praise.

"David has been with me from the start of this enterprise, running for president," Obama said, adding: "If it were not for him, we would not have been as effective as a White House, and I probably wouldn't be here."