Who is Barack Obama closest to on Capitol Hill? Ask any well-connected Congressional aide, and the most likely response will be, “I don’t know.”

[IMGCAP(1)] He was the first Senator elected president since 1960. But his personal ties on the Hill are not well known.

Obama, many point out, was really only a member of Club Senate for two years after taking office in January 2005, skipping town at the beginning of 2007 to run for president.

He never had time to ensconce himself in Washington, D.C., and with his family in Chicago, he was not one to linger and schmooze.

Further, he has scooped up a few of those whom he was closest to and brought them into the administration. Former House Democratic Caucus Chairman Rahm Emanuel of Illinois has known and touted Obama for years, and he will now be White House chief of staff. Former Sen. Joseph Biden (D-Del.) will, of course, become vice president at noon today.

So it’s “I don’t know” in first place. The second most likely response: “Beyond my boss, I don’t know.” And the third: “Richard Durbin.”

By all accounts, the Senate Majority Whip and Obama are not just allied Illinois Democratic pols but are personally close.

The two had a private lunch soon after Obama was elected, and Durbin can be expected to continue in his role as a counselor. They’ve sponsored legislation together. Durbin pushed Obama to run for president before it was cool, endorsed him before any other Senator did and, now that Obama is elected, describes himself as the “First Friend.” Durbin will have unusual influence, being by rank the second most powerful Senator as well as the buddy of the commander in chief.

There are a handful of others who can walk the corridors of Capitol Hill bathed in a similar light, knowing they, too, are FOOs, or Friends of Obama.

Sen. Claire McCaskill (D-Mo.)

McCaskill took a huge risk in January 2008 when she endorsed Obama for president. Not only did she reject the entreaties of another female Democratic Senator who was running — that of course being Hillary Rodham Clinton of New York — but she got behind Obama at a critical moment, just after he lost in New Hampshire and only a couple of weeks before the Missouri primary, which he then won. He had appeared in Missouri multiple times on her behalf during her hard-fought 2006 victory, and the two became close after she landed in the Senate.

Sen. Kent Conrad (D-N.D.)

After Durbin, Conrad was the second Senator to endorse Obama, backing him just before the Iowa caucuses. Conrad, known to other Senators for occasional impishness, took to Obama early on and developed an easy way with him, on occasion “mercilessly teasing” the earnest new Senator, according to a Conrad aide. The two have the type of rapport that Conrad will be able to serve as a “truth teller,” according to the aide, as well as help out with fiscal matters that are the Budget chairman’s forte. A phone call last week began with Obama exclaiming, “Hey bro!”

Sen. Dick Lugar (R-Ind.)

Obama and Lugar have worked closely on the Nunn-Lugar program to dismantle and secure weapons of mass destruction in the former Soviet Union as well as on extending the initiative to conventional weapons. During a trip by Lugar last month to Moscow, Russian leaders were aware of his ties to Obama and were extra attentive, according to a Lugar aide. Lugar can be expected to assist Obama on foreign policy and serve as a conduit to foreign leaders, particularly to the Russians as Obama seeks to improve relations. The two bonded on an August 2005 inspection tour, during which their plane was detained at a Russian airport. Obama showed early signs of coolness under fire: Along with Lugar, he took a nap.

Sen. Tom Coburn (R-Okla.)

Yes, Tom Coburn. The perennial thorn in the side of Majority Leader Harry Reid (D-Nev.) took a liking to Obama and views him as a straight-talker, a high compliment from the very direct Coburn. The two got to know each other while teaming up to pass legislation creating an Internet database of federal spending.

Sen. Bob Casey (D-Pa.)

Obama is also on good terms with Sen. Bob Casey (D-Pa.), who endorsed him just before the Pennsylvania primary. Obama lost but didn’t forget it.

Obama has relationships with several House Members, including various people in the Illinois delegation. He also has connections in the Congressional Black Caucus, including early backers Elijah Cummings, (D-Md.) and Artur Davis (D-Ala.). Obama and Davis attended Harvard Law School at the same time.

Key House contacts include:

Rep. Jesse Jackson Jr. (D-Ill.)

Obama has a long relationship with Jackson, another presidential campaign co-chairman who backed him for the Senate in 2004 after Jackson himself decided not to run. Jackson’s sister, Santita, has been friends with Michelle Obama since they were in school together in Chicago.

Rep. Henry Waxman (D-Calif.)

The House Energy and Commerce chairman is not known to be particularly close to Obama. But his longtime aide, Phil Schiliro, is Obama’s legislative affairs chief. Not bad for Obama, considering all his massive health care and energy projects will have to move through Waxman’s committee.

Rep. Jan Schakowsky (D-Ill.)

Schakowsky got to know Obama when the two served contemporaneously in the Illinois legislature. Not only was she an early backer for his presidential run — before even he was — but she also supported his bid in 2004 for the Democratic nomination for Senate.

Sometime before the day of the vote, she says, she was at the White House for a meeting. Noticing a look of horror on President Bush’s face, she realized he was mistaking her “Obama” button for an “Osama” button. After she explained, Bush said, “I don’t know him.” Schakowsky replied, “You will.”