Sen. Bob Corker’s impending departure removes from many critical debates on Capitol Hill an influential, dealmaking, establishment Republican who can bend the president’s ear — but his exit will arguably be felt most acutely in the realm of foreign policy.

The chairman of the Senate Foreign Relations Committee, Corker (R-Tenn.) has earned accolades as one of the body’s most committed champions of bipartisanship. In his tenure, he has also spearheaded many efforts to reestablish Congress’s authority in diplomatic matters that, over decades, it had ceded to the executive branch.

Grappling with a divided Congress and an ideologically separate White House poses complicated diplomatic challenges, and Corker has tangled with both former president Barack Obama and President Trump over matters as varied as nuclear proliferation, sanctions and the course of foreign wars. Corker has relied on a combination of personal diplomatic skills: acerbic wit, folksy Tennessee drawl, and, sometimes, blunt criticism of politicians who outrank him.

But it is not entirely clear how his heir apparent, Sen. James E. Risch (R-Idaho), who is a more stoically partisan Trump supporter, or his understudy, Sen. Marco Rubio (R-Fla.), who has been tested on national political stages but is less experienced in the Senate, would approach the job. Risch and Rubio are next in line in terms of seniority on the committee.

Corker said Tuesday that he was staying out of the fight to succeed him — save for placing a quick call to Risch on Tuesday to joke that he must be “the happiest person in the United States,” other than Corker’s family. (And — also jokingly — to tell Risch he could stop thinking about poisoning Corker’s coffee to get the chairman’s gavel.)

Sen. Bob Corker speaks with reporters on Capitol Hill on Sept. 26, 2017, after announcing his retirement at the conclusion of his term. (Aaron P. Bernstein/Reuters)

“I hope that we have established a standard that will prevail,” Corker said of his bipartisan legacy. “That was the goal. And to try to take other people’s views into account and pull people together and make sure our foreign policy is something we stay united on.

“But each person, you know, everybody here, has their own election certificate, and each person decides how they’re going to conduct themselves,” he added.

Corker has been the GOP’s top foreign policy voice for the entirety of the debate over the Iran deal. He linked arms with Sen. Benjamin L. Cardin (D-Md.) early on to codify a unique opportunity for Congress to reject the multilateral nuclear pact with Tehran. Though Corker opposed the deal vehemently, he stuck to the terms of the deal that was struck, effectively presiding, in 2015, over its preservation.

Next month, it will be up to Corker to again steer the Iran deal — or not — through its next challenge, should the president refuse to certify that Tehran is in compliance with that nuclear deal, as many suspect he will.

“We kind of know what’s going to happen, and we’ve been working closely with him,” said Corker, who has remained silent about the details of Trump’s plans but insists he has been “working hand-in-glove with the administration on this and have been for some time.”

Cardin said in a statement Tuesday that he was personally saddened by the news of Corker’s retirement, commending his colleague for “the enduring belief that the foreign policy of the United States should always be conducted in a bipartisan, sober, values-based manner.”

But Corker has at times drawn the criticism of his colleagues for appearing to be too close to Trump. He is in more regular touch with Secretary of State Rex Tillerson than any of his Senate colleagues, and Corker has fairly regular contact with the president (including on Tuesday, when they spoke about his retirement). At one point, Corker was on the shortlist being considered for vice president; at another, his name was being tossed around as possible secretary of state. (Corker says he is not eyeing a position in the administration — or getting into any sort of political race closer to home.)

Corker fielded such criticism earlier this year, for standing in the way of senators who wanted to pursue stiffer sanctions against Russia and to check the president’s ability to ease existing sanctions against Moscow. For months, Corker held back a burgeoning effort to pass Russia sanctions bills — something he later explained he did to give Tillerson a chance to make a deal with Russia to make strides in the Syrian war.

But when Corker lost his patience with the administration, he became one of Congress’s champions for more punitive measures, and the congressional review power many sought, to the Trump administration’s great annoyance.

It would be a model, Corker said, for how Congress would get back in the ring on sanctions measures in the future, predicting that North Korea would be the next country over which Congress would write into law the power for itself to check the president.

Corker changed his mind when North Korea’s nuclear tests became too “acute,” in his words, to go it alone.

Corker has been celebrated as a dealmaker in foreign relations and has made a practice of flying in at the last minute to cobble together compromise arrangements to pull more Republican votes on board. He did it as a first-term senator with the New START treaty, which regulates the type and number of nuclear warheads the United States and Russia are allowed to have. He did it against in 2013 with the comprehensive immigration bill.

But sometimes Corker’s dealmaking has meant allowing debates to proceed on matters with which he hasn’t fully agreed. Corker maintains that a new authorization for military force is not necessary to fight the Islamic State, but he has promised Sens. Tim Kaine (D-Va.) and Jeff Flake (R-Ariz.) that their proposal to reauthorize combat against extremist groups will get time in his committee. Corker has also let himself be persuaded on other matters — such as when Congress voted overwhelmingly to allow the families of Sept. 11 victims to sue the Saudi government over support for terrorists who perpetrated the attacks, though Corker had reservations about the global security implications of such a move.

One place, however, where Corker has been very consistent is in his efforts to get Congress to pay more attention to matters of human trafficking and modern-day slavery. His efforts to address modern-day slavery caught the attention of presidential daughter Ivanka Trump earlier this year, and the State Department recently pledged to dedicate $25 million to the Global Fund to End Modern Slavery — a figure that British Prime Minister Theresa May soon matched. Corker hopes that the president will embrace the cause, as well, and that it gains more momentum — preferably before Corker departs the Senate.