The Senate has displayed a general deference toward the Obama administration’s foreign policy in the past four years, but it could become a far more raucous and combative place if Foreign Relations Chairman John Kerry is tapped to join the Cabinet.

The Massachusetts Democrat is on President Barack Obama’s short list for secretary of State or Defense, and Kerry would almost certainly breeze through confirmation (unlike another possible nominee for State, U.N. Ambassador Susan E. Rice).

But the White House may start to have second thoughts about nominating Kerry as it envisions a chamber that could be more willing to challenge Obama on a range of issues, from Iran to Cuba.

If Kerry leaves, the chairmanship of Foreign Relations would probably fall to Sen. Robert Menendez, the combative New Jersey Democrat. Although California Democrat Barbara Boxer stands next in line after Kerry in seniority, she is unlikely to give up her position as chairwoman of the Environment and Public Works Committee.

“If the chair opens up, it will go to Menendez, no question,” said a Democratic member of the committee, who spoke on condition of anonymity to discuss internal committee dynamics.