Voters in the Democratic primary in New Jersey on Aug. 13 for the United States Senate are lucky to have a choice among four candidates with solid credentials: two with experience in Congress and good voting records; one who has worked hard at the state level on women’s issues, in particular; and one who made a national name for himself by bringing new thinking, honesty and compassion to the hidebound, corrupt and cold city government in Newark.

The four are running for the party’s nomination to replace Senator Frank Lautenberg, who died in June. We strongly believe the best choice is Mayor Cory Booker of Newark, who will be able to use his political star status to fight for the neglected, the powerless, people who are working and people who need to work in New Jersey and nationally. He wants to battle obesity, and the guns that kill and maim so many. And he wants to round up more support for the urban centers where more and more Americans live.

Ambitions are easy to come by, but Mr. Booker doesn’t just talk about helping the helpless. He does it. He would bring a sense of reality and some street-level experience to a Senate that often seems disembodied from the whole planet.

Mr. Booker’s opponents are also known for having progressive records. Sheila Oliver, the speaker of the State Assembly, has worked hard to promote women and women’s issues in the male-dominated state power structure. Representative Frank Pallone Jr., who is supported by the Lautenberg family, helped write the Affordable Care Act. Representative Rush Holt is not only the most able legislator among them, but he is also a teacher and scientist. Those backgrounds are in short supply in a House of Representatives too often driven by emotionalism and fact-free politics — especially on issues like climate change.