Dianne Feinstein will be rightly remembered as a trailblazer—the first woman to serve as mayor of San Francisco and the first woman elected to the Senate from California. But once she broke those barriers and walked through those doors, she got to work. I first got to know Dianne in the Senate, where she was a fierce advocate for gun safety measures and civil rights. Later, when I was president, I came to rely on her as a trusted partner in the fight to guarantee affordable healthcare and economic opportunity for everyone. The best politicians get into public service because they care about this country and the people they represent. That was certainly true of Dianne Feinstein, and all of us are better for it. Today Michelle and I are thinking of her daughter, Katherine, and everyone who knew and loved her.