A. She was key to many achievements, including building the international sanctions regime against Iran, the most effective in history and the single factor that forced Tehran to the negotiating table, making possible last year’s agreement that set back Iran’s nuclear program by well over a decade; overseeing the negotiation of a new arms control treaty with Russia that reduced nuclear stockpiles to their lowest levels in decades; and brokering a cease-fire in Gaza that averted a ground war. She played a central role in bringing China and India to the table for the first time on climate change, leading to last year’s Paris accord; in opening Burma to the world and taking the initial steps that resulted in normalized relations with Cuba; and in advancing the rights of women and girls around the globe.

But in my view, her greatest achievement was her work with the rest of the national security team that prevented any attacks by an international terrorist group on the homeland. This is a remarkable achievement, given the intentions, capabilities and plots of Al Qaeda to attack us during her tenure. Secretary Clinton was a leader in our fight against terrorism. In these policy discussions, her voice carried immense weight. She supported aggressive operations against extremists, including drone strikes, the military surge in Afghanistan and the Bin Laden raid. In her diplomatic work, she worked to ensure that our allies and partners were supporting us in this critically important mission.

I think it is ironic that many of Secretary Clinton’s critics, who are raising questions today about her achievements as secretary of state, heaped praise on her both when she was in the job and when she stepped down at the end of President Obama’s first term. In 2012, Senator Lindsey Graham, Republican of South Carolina, said she was “one of the most effective secretary of states … that I have known in my lifetime.” A year earlier, Mr. Graham called her a “national treasure.” In 2014, Mike Huckabee, a former Republican governor of Arkansas, called Secretary Clinton “a policy genius.” Even Newt Gingrich, in 2013, said that she had done a “tremendous job” as secretary of state.

Q. Some people have responded to your op-ed by highlighting your work for Beacon Global Strategies, which was co-founded by former associates of Mrs. Clinton, and charging that this compromises your endorsement. How do you respond?

While I largely agree with Mr. Morrell’s analysis and conclusions (although I do not share his enthusiasm for pursuing ISIS into Syria), I also think it’s fair to point out that his employer, Beacon Global Strategies, has strong ties to Hillary Clinton.” — Anetliner Netliner, Washington, D.C. area