1) “Riverdale” finale, 9 p.m., CW. For decades, CW has been the home of shows based on comic books or youth novels. Now, under new owners, that era is ending. “Riverdale” (shown here) has had strong production and solid acting (especially by Lili Reinhart as Betty), but bizarre plot twists. This season, the characters slid back to the 1950s, then returned. Now we flash forward; Betty is 86 and wants to relive the final day of her senior year.
2) “Nancy Drew” finale, 8 p.m., CW. It was back in 1930 that Nancy first showed up in a book, snooping for clues. There have been hundreds more books, plus six movies, three series, a TV movie, comic books and more. In this version, Nancy (played with subtle skill by Kennedy McMann) is out of school and saving her troubled town. Tonight, CW says, she has “her most shocking discovery yet” and resolves her romance with Ace.
3) Republican debate, 9 p.m. ET, Fox News. The debate season gets a high-stakes start. In Milwaukee – savoring Wisconsin’s status as a swing state — Republican challengers gather. Most have avoided commenting on Donald Trump’s four indictments on 91 felony charges; now the anchors (Bret Baier and Martha McCallum) will be in charge.
4) “MasterChef,” 8 and 9 p.m., Fox. The first hour has chefs tryingto turn military rations into something tasty. The second stirs some fun, with duos switching chefs every 10 minutes. One contestant chooses the duos, with a mischievous touch: The sharpest personalities are paired; so are the quietest ones. The strongest chef is paired with the weakest. Semi-chaos follows, in interesting ways.
5) “Abbott Elementary,” 8-10 p.m., ABC. Now that “Wonder Years” has finished its season, this likable comedy reruns four of its key episodes. That starts with the season-opener (preparation week for the teachers) and ends with the arrival of Janine’s estranged mother, played by Taraji Henson.