LOS ANGELES — Los Angeles has the biggest jail system in America and sends people to state prison at almost four times the rate of San Francisco, even though violent crime has fallen in both cities. And there has not been a death penalty case in San Francisco in decades, while prosecutors in Los Angeles are still seeking new capital cases after Gov. Gavin Newsom issued a moratorium on executions.

San Francisco and Los Angeles may share a similar brand of liberal politics. They are both led by mayors who see it as their jobs, in part, to push back against President Trump’s agenda, and both cities are trying to bring liberal solutions to bear on some of the same problems, like homelessness and housing.

But when it comes to criminal justice, the two cities could not be more different.

[Sign up for our daily newsletter about news from California here.]

“They are polar opposites,” said Patrisse Cullors, a co-founder of Black Lives Matter.

Now, those competing approaches — pushing to reform mass incarceration versus a more traditional get-tough-on crime tack — are likely to clash in the race for district attorney of Los Angeles. George Gascón, the district attorney of San Francisco, is weighing a return home to Los Angeles, where he was a police officer in the 1990s, to challenge Jackie Lacey, Los Angeles’s incumbent top prosecutor, setting the stage for what activists and experts say will be the most important district attorney’s race in America.