Rubio Is in Spotlight on Second Big Day of Cabinet Hearings

When President-elect Donald J. Trump’s choice for secretary of state, Senator Marco Rubio of Florida, appears before the Senate Committee on Foreign Relations today, it may be easy for him to persuade senators that he can lead American diplomacy at a moment of unusual global turmoil.

The harder task may be convincing them that he can credibly represent a president with whom he has a long history of personal and policy differences.

As a third-term senator who holds generally mainstream foreign policy views, Mr. Rubio, 53, is expected to be confirmed with relative ease later this month after Mr. Trump, once inaugurated, officially nominates him to succeed Secretary of State Antony J. Blinken.

Unlike several of Mr. Trump’s other top cabinet picks, Mr. Rubio has decent relations with his fellow Senate Democrats, no scandalous allegations about his personal behavior and relevant policy experience. He serves as vice chairman of the Senate Intelligence Committee and is a member of the committee that will question him.

Even senior Biden administration officials believe that Mr. Rubio can be a responsible leader of the State Department as the Trump administration confronts a roiling Middle East, the war in Ukraine and looming threats from China.

The bigger questions revolve around Mr. Rubio’s relationship with the incoming president.

The two battled for the 2016 Republican presidential nomination in a duel that began with policy differences and descended into mutual personal ridicule. Mr. Rubio declared Mr. Trump an unfit-for-office “con artist,” and even mocked his manhood, accusing his rival of having “small hands.” In response, Mr. Trump derided Mr. Rubio as a scripted establishment politician and taunted him as “Little Marco.”