WASHINGTON -- Most White House jobs are self-explanatory: Chief of staff. Press secretary. National security adviser. Then there is the job of "senior adviser" -- as influential as any, and more than most, but the sort of post whose duties change with each new occupant and his times.
And so it is now that President Obama has tapped as his new senior adviser Dan Pfeiffer, who follows in the hard-to-follow steps of the two Davids most closely associated with Mr. Obama's rapid rise, election and re-election: first David Axelrod, who left the White House two years ago, and then David Plouffe, whose final day there was Friday.
The transition last week draws attention to a West Wing office that at once has been crucial to Mr. Obama's presidency yet was nearly eliminated once he was re-elected and Mr. Plouffe (pronounced Pluff) kept to his plans to leave the administration.
For the president's first two years, Mr. Axelrod, 57, who is extroverted and disorganized, was the protector of the Obama brand, overseeing the president's shift from campaign platform to governing agenda on all issues -- and doing so amid an economic crisis that forced unanticipated actions like an $800 billion stimulus package and an overhaul of financial industry regulations.
For the past two years, the introverted and hyper-disciplined Mr. Plouffe, 45, served as what he called "the connective tissue" between the administration and the re-election campaign, making sure that the actions of one did not threaten the success of the other.
In November, with the president re-elected and his second-term agenda defined, Mr. Obama and close advisers initially wondered whether he needed a successor to Mr. Plouffe. Mr. Obama decided that he did -- someone who could continue to take the long view, while others managed the daily distractions of their particular portfolios, domestic or international.
"The president does want someone who's thinking down the road a little bit -- it's hard to describe," Mr. Plouffe said in an interview. "The role is really to make sure you're thinking about things strategically, you're thinking about the next move or two or three, you're providing some guidance on messaging."
Of Mr. Pfeiffer, who is 37 and has been Mr. Obama's communications director, Mr. Plouffe said: "Ultimately Dan's going to be someone who's going to be looked at most authoritatively to describe how a certain strategy would unfold, what the downsides are, what the trap doors are. You can't really look at it as a direct replacement. Even Axe and I, we didn't do exactly the same thing."
The job of senior adviser -- equal parts counselor, confidant, strategist and truth-teller -- is not new to the Obama White House, yet it is a relatively modern invention.
The presidential historian Michael Beschloss cites as an early model Louis Howe, who guided the polio-stricken Franklin D. Roosevelt back into politics and ultimately the presidency and was so close a White House counselor that he stayed in the Lincoln Bedroom. But Mr. Beschloss said the role of an in-house strategist took root with President Richard M. Nixon and his reliance on his longtime aides H. R. Haldeman and John D. Ehrlichman.
More recent examples that he and others cite include George Stephanopoulos and Paul Begala, who were aides to President Bill Clinton, and President George W. Bush's advisers Karen Hughes, Karl Rove and Dan Bartlett.
The near institutionalization of the job reflects "the whole idea of the permanent campaign," Mr. Beschloss said. "Presidents have come to recognize that they do not have to worry about politics and their message only in election years."
By definition, a common attribute of these advisers seems to be enjoying a relationship of trust and familiarity, even intimacy, formed with a president by shared experience on the bumpy road to the White House.
"An important thing is to view decisions through the prism of 'Is this true to who we are?' " Mr. Plouffe said. "And that's kind of an instinctive thing, a judgment on 'Is this consistent with what we campaigned on, and who he is?' "
While Mr. Plouffe and Mr. Axelrod have worked longer for Mr. Obama, Mr. Pfeiffer is one of "the originals," as aides refer to those who have been with the president since at least January 2007, when he began his race to the White House. Fewer remain for the second term -- among them Denis McDonough, designated as the new chief of staff; Alyssa Mastromonaco, deputy chief of staff; and the presidential assistants Valerie Jarrett and Pete Rouse -- which lent weight to the argument for keeping a senior adviser, someone with institutional memory, aides said.
While the stylistic differences between Mr. Axelrod and Mr. Plouffe were evident, Mr. Pfeiffer is similar enough to Mr. Plouffe -- reserved, competitive and obsessed with how Americans get information online -- that White House colleagues joke, "You're going from one guy from Delaware with lots of P's and F's in his name to another."
Mr. Obama, in a surprise public farewell to Mr. Plouffe on Friday, said that "were it not for him, we would not have been as effective a White House, and I probably wouldn't be here."
In the interview, Mr. Plouffe said, "The first thing I'm going to do is go spend a lot of time with my family," including taking his son, Everett, 8, and his daughter, Vivian, 4, to and from school. Then he will give speeches, consult with private sector clients "and leave time to help him" -- the president -- "from the outside, unofficially."
While Mr. Plouffe is likely to be courted by Democrats running for the presidential nomination in 2016, he said he was done with presidential campaigns: "I think that -- and I presume David would say the same thing -- you'll never top this."
This article originally appeared in The New York Times.