Tonight will not mark the final episode of “Law & Order” (9 p.m., NBC). The legal drama survives to air another day, and that day will be Sundays, beginning in January after NBC ends its Sunday Night Football run.

That’s just as well, because tonight’s 17th season-ender does not have a valedictory air about it. But like any good finale, it sets up scenarios for the possible departure of major characters.

Harry Hamlin guest stars as the politician patriarch of a seriously messed-up dynasty. The shocking murder of his alcoholic ex-wife after a charity fundraiser casts a harsh spotlight on the pol, his disturbed daughter and his drug-addicted son. Jeffrey Tambor guest stars as a biased and clueless judge who owes obvious favors to Hamlin’s crooked character.

This bit of stunt casting provides a nice coda on the shambles of NBC’s lamentable season. As you may recall, Tambor also played a judge in the short-lived sitcom “Twenty Good Years,” which co-starred John Lithgow and premiered only last fall.

So who could be leaving “Law & Order”? In tonight’s episode, Cassady (Milena Govich) runs afoul of Van Buren (S. Epatha Merkerson), and McCoy (Sam Waterston) feels ill-used by Branch (Fred Thompson).

It’s no secret that some Republicans would like Thompson to run for president. And that would certainly end his “Law & Order” career.

The writers of tonight’s episode had fun winking at the curious notion of one of their own making a bid for the White House. Why else refer to Hamlin’s over-the-top villainous character as an “ex-senator and presidential candidate”?

At one point, McCoy and Branch share a cryptic exchange that seems to comment on matters that transcend the scope of their fictional roles. “One day, this chair is going to be empty,” Branch says. McCoy retorts, “I’m no politician, Arthur.” To which Branch replies, “Yeah (pause), everybody says that.”

¢ Long the province of church basements and played by grandmothers with idle time and loose change on their hands, bingo has suddenly gone high tech. “National Bingo Night” (8 p.m., ABC) allows players to download and print their own bingo cards from ABC.com and play along with a studio audience.

While the audience members are trying to reach bingo the old-fashioned way, a contestant is trying to win $50,000 by guessing the value of the numbers in play.

Like every game show set since “Millionaire,” “Bingo” straddles the line between futuristic fantasy and over-caffeinated spectacle. And like “Deal or No Deal” host Howie Mandel, “Bingo” host Ed Sanders has sacrificed his locks for his job.

Tonight’s other highlights

¢ CBS celebrates longtime broadcaster Walter Cronkite on “That’s the Way It Is: Cronkite at 90” (7 p.m., CBS).

¢ Scheduled on a two-hour “Dateline”78 p.m., NBC): an update on a moonlit murder case.

¢ Ozzy Osbourne performs on “Friday Night SmackDown!” (7 p.m., CW).

¢ Technology editor David Pogue discusses new developments and answers frequently asked questions about gadgets and more on “It’s All Geek to Me” (7 p.m., Science).

¢ A pop psychologist confronts an abusive father behind bars on “A Dr. Phil Primetime Special” (8 p.m., CBS).