Of course we did not always see eye-to-eye, even on our own bill. There was one period when John and I knew we had to scale back our more ambitious campaign-finance legislation to attract support. We had a tense and difficult conversation about what should be cut, and it didn’t end well. I spent the evening afterward wondering whether we might go separate ways, even though, despite our ideological differences, we had reached the same conclusion: that the system by which members of Congress were being elected was corrupt.

By this time, John and I were no longer just a political odd couple. We had become dear friends. When I approached John on the Senate floor the next morning to agree to much of his version of a scaled-back McCain-Feingold bill, I was struck and humbled by the relief on his face. We laughed when he hugged me and patted me on the back repeatedly. John also agreed to some of my requests in that conversation, conveying a keen understanding of why I was fighting hard for certain provisions.

One time, during a long, lonely debate before we had nearly enough votes, we sat together on the Senate floor and commented about how our colleagues in each of our parties weren’t speaking to us much anymore. I said, “Yeah, and now you’re going to become president and leave me here alone.” John replied, “No, no. You’ll be in the cabinet.” He paused and then, with a grin, said, “But just not as secretary of defense.”

And, indeed, while we often agreed on domestic reform issues, we had almost diametrically opposed views on defense, especially on certain military interventions, Iraq in particular. But this did not stop John from inviting me as one of two Democrats on a nine-person congressional delegation trip to Iraq in 2006, when things were not going at all well there. On the plane trip over, he had us all convene for a briefing. John spoke at length about the approach of Col. H.R. McMaster, who would later become a three-star general and President Trump’s national security adviser, to insurgencies. At the appropriate time, I interjected my views about the likely futility of such an approach, to which a Republican governor on the trip said: “Why did you bring this guy along?” Not missing a beat, John responded: “I bring Russ along because he is consistent — consistently wrong.” The fact is, as passionate as John was about his positions, he truly valued hearing all sides and was a good listener.

Yet, it was John’s interaction in Baghdad’s Green Zone in 2006 with David Petraeus, then a lieutenant general, that most displayed his integrity and commitment to getting things right. John’s questions to the decorated general were pointed and tough and made clear his first duty was to the American men and women serving there, not to his own ego or belief in the mission. He sharply challenged the general’s claims about the success that had been achieved in training Iraqi troops. He did this in front of strong opponents of the war knowing it could be used as fodder against the intervention in which he believed. He wanted to know the facts wherever they led.