President-elect Donald Trump’s potential Cabinet picks have stolen the spotlight, but one lesser-known job may prove to be among the most crucial to the incoming administration’s success, or failure, on Capitol Hill.

The new head of the White House legislative affairs office will serve as the primary liaison between lawmakers and the president. If the Trump administration is to enact its policies, it will rely on the unit to keep members and congressional staff in the loop day-to-day and to ferry intelligence back to 1600 Pennsylvania Ave.

That role will not fall to Vice President-elect Mike Pence, a former House member from Indiana, or to White House Chief of Staff Reince Priebus, who is close to House Speaker Paul D. Ryan, though they will certainly make the rounds on Capitol Hill.

The job will go to the legislative affairs office.

Numerous sources who spoke both on the record and some on condition of anonymity said Rick Dearborn, chief of staff to Alabama Republican Sen. Jeff Sessions and a Trump campaign insider, may be first in line for the legislative affairs job. Staffing decisions in the Trump administration still are in tremendous flux. Dearborn could also follow Sessions to a Cabinet department, since Sessions has been linked to jobs such as Defense secretary and attorney general.

No matter who fills the White House job — officially known as assistant to the president for legislative affairs, and not subject to Senate confirmation — it will be a pivotal conduit between the two branches of government. President Barack Obama’s office, at times, drew criticism, even from Democrats, for not cultivating good ties with Congress.

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“Having a good strong congressional relations office is almost as critical as making your Cabinet selections and using them in the proper way,” said former Senate Majority Leader Trent Lott, who is now a lobbyist at Squire Patton Boggs.

The Mississippi Republican added that having a high-profile former lawmaker in the job would also serve the Trump administration well. “The main thing is to have somebody that knows the players and could actually go in and sit down with Chuck Schumer,” he said, referring to incoming Senate Minority Leader Charles E. Schumer of New York.

Nick Calio, who held the top legislative affairs job for George W. Bush and his father, said next year’s policy agenda of tax cuts and infrastructure spending “magnifies the role of this office” and makes it more important.

“When you’re handling the role the right way, you’ll be yelled at on Capitol Hill for what the president’s doing and yelled at at the White House for what Capitol Hill is doing,” Calio added.

Lawmakers of both parties agree that the job of managing the Hill-White House relationship will be critical in the 115th Congress since the president-elect has no government experience and few ties to lawmakers.

“Who they tap for legislative affairs is, eventually, significant,” said Sen. Brian Schatz. But, the Hawaii Democrat added, “I’d say that’s like an eighth-order problem at this point,” noting bigger issues such as filling the Cabinet and personnel turmoil on the Trump transition team.

The most senior GOP senator, Orrin G. Hatch of Utah, who chairs the tax-writing Finance Committee, said he suspects the Trump administration will reach out to Congress, soliciting “ideas from both sides.” Trump, he added, “is a very candid, intelligent man,” whom Hatch expects to keep open communication with the Hill.

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When Obama began a pitch to lawmakers to move a trade-promotion measure, the White House made the highly unusual decision to tap a K Street denizen, Marty Paone, as the chief liaison to the Senate. The onetime aide to Senate Minority Leader Harry Reid of Nevada received a rare waiver to join the Obama administration despite its prohibition on registered federal lobbyists.

The waiver, granted in late 2014, stated that bringing on Paone served the public interest because the job “requires a candidate who possesses deep and long-standing relationships in both parties in order to facilitate dialogue between the Senate and the White House.”

The Trump transition team did not respond to requests for comment. The president-elect’s transition office announced Wednesday that people who join the administration will be banned from lobbying for five years after leaving government. All appointees will be required to sign a form that they will abide by the ban.

The legislative affairs office, when managed effectively, is a hub of relationship-building on both sides of the aisle, said Kathryn Lehman, a former House GOP leadership aide during George W. Bush’s presidency.

Bush’s legislative affairs team, she added, was “very, very visible to everyone on the Hill. You saw those people every time there was a vote. They knew which members went into which entrance to vote.”

Similarly, she said, they got to know details of lawmakers’ lives, asked about their families and invited them to lunch at the White House Mess, the dining room on the ground floor of the West Wing.

“You don’t want the first time you’re talking to a member of Congress to be when you need something from them,” added Lehman, now a lobbyist with Holland & Knight.

Whether the Trump White House will tap Dearborn to run the legislative affairs team is uncertain, though his allies on K Street say he’d be an ideal pick. Dearborn worked for Lott, served as assistant secretary for congressional and intergovernmental affairs at the Energy Department during the George W. Bush administration, and was appointed Sessions’ chief of staff in late 2004. Before joining the Energy Department, Dearborn was Sessions’ legislative director.

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Most recently, he has been viewed as the Trump campaign’s “eyes and ears in Washington, trying to develop relationships with people on K Street, in think tanks and other congressional offices,” said Cesar Conda, a lobbyist with Navigators Global.

Dearborn is connected to numerous lawmakers and their aides dating back decades. He and Ryan worked together for former Sen. Bob Kasten, including on the Wisconsin Republican’s unsuccessful 1992 re-election effort.

“During Kasten’s re-election campaign, we all shared this crummy one-bedroom apartment outside of Milwaukee,” recalled Conda, referring to himself, Ryan and Dearborn.

Trump will need someone running White House legislative affairs “who can open the doors and has those relationships,” said Conda, also a former chief of staff to Florida GOP Sen. Marco Rubio. “Rick is a longtime Senate chief of staff. Senators know him. Chiefs know him. He was always helpful to new chiefs coming in, so he has a lot of goodwill.”