The rewarding and intelligent documentary series “30 Days” (9 p.m., FX) begins its second season by confronting immigration, arguably the most contentious issue on the American political agenda.

For the uninitiated, “30 Days,” created by “Super Size Me” director Morgan Spurlock, invites participants to walk a mile, or rather a month, in another person’s shoes. In season one, a participant spent time with a Muslim family, and a responsible mother went on a bender to show her children just how frightening such behavior can be.

Spurlock brings a real sense of empathy to “30 Days” and allows individuals to emerge with all of their surprising quirks intact. “30 Days” is reality television for people who still use their brains and who remain open to changing their minds.

In tonight’s episode, Frank George, a member of the paramilitary Minuteman group dedicated to ending illegal immigration, agrees to spend a month living with the Gonzales family, a Mexican-American couple and their children, who share a tiny apartment.

The hour, and the month, is an emotional experience for both Frank and for viewers and a valuable contribution to our national conversation about immigration.

¢ The “American Masters” (8 p.m., PBS) profile “Walter Cronkite: Witness to History” offers both a brief biography of the acclaimed newsman and a survey history of TV journalism. As a print journalist covering World War II, Cronkite was there on D-Day, flew on bomber missions over Germany and covered the Nuremburg War Crimes trials. “Witness” follows Cronkite and the fledgling medium of television from the late 1940s to his retirement in 1981.

Tonight’s talent-show glut

¢ The auditions continue on “Rock Star: Supernova” (7 p.m., CBS).

¢ The top 10 are whittled down to eight survivors on two hours of “So You Think You Can Dance” (7 p.m., Fox). The first hour is a repeat.

¢ “The One: Making a Music Star” (7 p.m., ABC) continues.

¢ Regis Philbin hosts “America’s Got Talent” (7 p.m., NBC).

Tonight’s other highlights

¢ A serial killer may complicate a mob investigation on “Criminal Minds” (8 p.m., CBS).

¢ An assault on Sun raises the fear level on “Lost” (8 p.m., ABC).

¢ “Nightmares and Dreamscapes” (TNT, TV-14) offers back-to-back mysteries starring Tom Berenger and Marsha Mason (8 p.m.) and Jeremy Sisto and Samantha Mathis (9 p.m.).