Stephen Chernin / Getty Images Senator Robert Menendez

When John Kerry is confirmed to succeed Hillary Clinton President Obama’s Secretary of State, as he’s expected to be in the coming weeks, he will leave the gavel of the Senate Foreign Relations Committee to Bob Menendez, a second-term New Jersey Democrat.

Rarely has such a transfer of power offered such a study in opposites.

Menendez, who is Cuban American, is the first Latino elected to the U.S. House and Senate from New Jersey and would become the first Latino chair of the Foreign Relations Committee. His rise to the top of a panel with broad authority to oversee U.S. foreign policy will mean new attention to relations with Central and South America, normally a diplomatic backwater. Menendez will be an Administration ally on immigration reform – he has offered reform measures year after year only to see them die in the Senate. But his new authority is likely to slow efforts to liberalize relations with Cuba; Menendez, 59, is fiercely pro-embargo.

Whereas Kerry had to wait nearly 30 years to become chairman, Menendez’s rise to the top in six is relatively meteoric. The job should fall to the next most senior Democrat, California’s Barbara Boxer, but Boxer has indicated she prefers to remain chair of the Senate Environment and Public Works Committee. Menendez will have the somewhat complicated job of overseeing the work that Kerry, his predecessor on the panel, does at State. The two men have convivial relations that will surely be tested in the coming years.

As the U.S. enters a critical stage in relations with Iran, Menendez represents the pro-Israel wing of the Democratic party — thanks in part to the large Jewish population in New Jersey — that has been pushing the President to get tougher on Iran. Menendez, along with Republican Senator Mark Kirk, co-authored sweeping sanctions last year against Iran that the Administration didn’t particularly want. And he has voiced reservations about Chuck Hagel, Obama’s nominee to run the Pentagon, because of Hagel’s past statements on Iran. “He certainly has been a strong voice on Iran sanctions and has been instrumental in overcoming Administration hesitation on the most recent sanctions bill,” says Mike Singh, managing director of the Washington Institute for Near East Policy.

Menendez also nearly brought down one of the Administration’s early jobs bills in March 2009 and placed holds on two of Obama’s nominees over an appropriations rider that would have eased travel restrictions to Cuba. Opponents of the embargo were hoping the time was right for liberalization of U.S./Cuba relations just as Rep. Ileana Ros-Lehtinen, a Florida Republican of Cuban descent, finally left the chairmanship of the House Foreign Affairs Committee, a perch from which she blocked many an effort to open up Cuba. “He’s reflected the Cuban-American community faithfully, but that community is changing,” says Larry Sabato, director of the University of Virginia’s Center for Politics.”Younger Cubans are less likely to oppose normalization of relations. Just look at Florida and the Cuban vote there; it’s much the same thing in New Jersey and New York. The Castro brothers will pass from the scene entirely before too long, and then I’d bet matters will move more swiftly.”

Menendez got his start working for Union City Mayor William Musto in the 1970’s. Menendez turned on Musto after he was indicted on corruption charges, testifying against Musto in a bulletproof vest. He later took Musto’s job and served in the New Jersey General Assembly and Senate before being elected to Congress in 1992. Menendez’s prolific fundraising – New Jersey is, after all, home to much of the nation’s financial sector – helped get him elected in 2002 conference chairman, the No. 4 position in House leadership. He won Jon Corzine’s Senate seat in 2006, and again rose quickly through the ranks thanks to his fundraising prowess. He chaired the Democratic Senatorial Campaign Committee in 2010, outraising Republicans $130 million to $115 million in a big GOP year. Though Democrats lost six seats, Menendez was credited with saving the majority.

Menendez was investigated by then U.S. Attorney Chris Christie on allegations of corruption, though charges were never filed. In January 2012, Menendez blocked the confirmation of Patty Schwartz, Obama’s nominee to the federal bench and the long-time partner of the head of New Jersey’s public corruption unit in the federal prosecutor’s office. Though Menendez denied it at the time, the New York Times reported that lawyers and judges in New Jersey believed he “was acting out of resentment” stemming from the embarrassing corruption investigation.

During his tenure as chairman, Kerry was careful to never cross the line from friendly criticism to friendly fire on the Obama Administration’s foreign policy. An op-ed pushing for greater engagement in Libya, or some pointed comments about the lackadaisical pace of the Middle East peace process was as far as Kerry went. Menendez, by contrast, has shown much more willingness to take on his fellow Democrats up Pennsylvania Avenue and a chairman’s perch gives him a bigger megaphone. “The central question about Menendez is whether he’ll moderate any of his views to accommodate his party’s President,” Sabato says. If not, he may soon find himself taking on not only Obama, but his predecessor.