American environmentalists are already hopeful that the longtime Massachusetts senator — one of the fiercest climate hawks in Congress — will put the brakes to TransCanada's Keystone XL pipeline, something Hillary Clinton's State Department seemed loath to do.
But there's a lesser-known cause that also distinguishes Kerry from Clinton: his tireless attempts to reunite a Boston-area father with his children after they were spirited away to Egypt three years ago by the boys' non-custodial mother, an Egyptian consultant whose family had close ties to ousted dictator Hosni Mubarak.
Kerry could face questions about the case from fellow senators on Thursday, when he's quizzed by the Senate foreign relations committee.
Kerry is currently the chairman of that panel and pushed through a Senate resolution last year demanding Egypt return the two boys to their father.
In 2009, Colin Bower had full, legal custody of his sons, then aged six and eight, when they were kidnapped by their mother, Mirvat El Nady, and taken illegally to Egypt. The FBI alleges El Nady unlawfully changed her childrens' names, acquired Egyptian passports, paid cash for a one-way plane ticket and abducted them.
Kerry has been actively involved in trying to reunite Bower with his sons, Noor and Ramsay, for the past three years. His efforts once included engaging in a heated argument with Mubarak.
"After my first calls and meetings with Secretary of State Hillary Clinton on Bower's behalf, my next call was to then-Egyptian President Hosni Mubarak," Kerry wrote in an opinion piece in the Boston Herald in September.
"It ended in a shouting match, as it became clear Mubarak would do nothing to intercede and, in fact, he was determined to protect the abductors who had ties to his corrupt, crony regime."
Since then, Kerry wrote, he's been working with Egypt's new regime to help Bower get his sons back.
"Tenacity and more is required to complete this job and help a nascent government in Egypt to see the importance of facilitating the return of two abducted children and ending the nightmare that Colin Bower is living each day," he wrote.
"The rule of law must mean something, and respect for law cannot end at a border."
In a recent interview, Bower said he's hopeful one of Kerry's first moves as secretary of state will be to step up efforts to reunite him with his sons.
"Every Tuesday, I speak with two of his chiefs of staff and they reiterate that his priority is getting this done," Bower said.
"He really slammed this through the Senate to be sure he was the one who was owning this issue, and he continues to be the one to say he's committed to resolving it. And there's more that you can do as a member of the cabinet than you can as head of the foreign relations committee."
One of the challenges facing Kerry, however, is the fact that many mid-level bureaucrats in Egypt are from the Mubarak era, Bower said. His ex-wife's family owns a lucrative yeast business and allegedly has ties to the military.
"The family was part of the Mubarak elite, and there are still holdover people in government from Mubarak's regime," he said.
Nonetheless, Bower remains confident that Kerry can and will get the job done.
"He can do that, he's a true diplomat. They're going to have to deal with Sen. Kerry for four years; they're going to want to build up some goodwill."
A Kerry aide said Tuesday that the lawmaker will continue to fight on Bower's behalf.
"Sen. Kerry remains deeply and personally invested in working to reunite Colin Bower with his sons and has been focused on this tragic case since shortly after the illegal abduction from Massachusetts," the aide said.
"He's urged the reunion of Colin and his boys to the highest levels of the Egyptian and U.S. government, and it will remain a personal priority."
Kerry has the backing of congressional Republicans. The Republican-controlled House of Representatives introduced a resolution on the custody dispute late last year.
"The resolution is not calling for anything extraordinary," Ileana Ros-Lehtinen, a Republican congresswoman from Florida, said on the House floor in late December.
"We are simply appealing to the Egyptian government to uphold its responsibilities and return these two boys to their rightful home."
Kerry's first overseas trip, however, isn't to Egypt but to Turkey, according to the Turkish daily Milliyet.
The newspaper reported on Monday that a visit to Ankara will be Kerry's first visit to a foreign country as secretary of state. He'll be there for talks on Iraq and Syria.