Television’s sweeps month often reminds us that the medium’s roots go back to the days of Variety Theater. Groucho Marx, a star of stage, screen and small-screen game shows, once defined TV as “Terrible Vaudeville.”

TV’s vaudeville roots can be seen every week when viewers get the chance to give their least favorite “American Idol” contestant the hook. Last Monday’s David Blaine spectacle harkened back to the days of Harry Houdini. And tonight, “Keith Barry: Extraordinary” (7 p.m., CBS) brings us the second card-trickster illusionist of the week.

A popular act in his native Ireland, Barry made a name for himself in this country in 2004 when he appeared on an MTV Spring Break special. On “Extraordinary,” he will deploy his talents for sleight-of-hand and illusion on a battery of celebrities, including Matthew McConaughey, Wilmer Valderrama, Rachel Hunter, Elijah Wood, David Krumholtz and Vivica A. Fox. He’ll also play a game of mind control with Jessica Simpson. Just how much mind he’ll have to control is anybody’s guess.

¢ Reese Witherspoon headlines the limp 2003 sequel “Legally Blonde 2: Red, White and Blonde” (7 p.m., Fox). Let’s hope her recent Oscar for “Walk the Line” convinces the capable Witherspoon to avoid forgettable fare like this in the future.

¢ A caustic combination of “The Office” and “Spin City,” the imported British comedy “The Thick of It” (8 p.m., BBC America) follows the workings of a government minister and his harried staff.

Don’t go looking for the high-minded speeches or policy wonkery of the departing “West Wing” or defunct “Commander in Chief.” The focus here is on minute-to-minute spin, survival and posterior covering, often over the most trivial and contrived matters. A minister reverses a long-held position at the behest of his superiors and uses painful and embarrassing anecdotes about his colleagues to back up his change in policy. He sends an obscene e-mail on his publicist’s computer and then browbeats her into taking the blame when its contents become public.

Half scripted and half improvised, “Thick” has the unrehearsed feel of “The Office.” The tone is much darker and deeply cynical, and the coarse language is blistering and relentless. Although it is a critical hit in its native land, many viewers will find it too dark and too filled with inside references to British politics to evoke even uncomfortable laughs.

Tonight’s other highlights

¢ A small-town basketball team fights for the state championship in the 1986 period piece “Hoosiers” (7 p.m., TCM), starring Gene Hackman, Barbara Hershey and Dennis Hopper.

¢ A Major Leaguer faces murder charges on “Close to Home” (8 p.m., CBS).

¢ As the staff juggles weddings, Ed’s CIA past comes back to haunt him on the season finale of “Las Vegas” (8 p.m., NBC). Wolfgang Puck, Dean Cain and Jerry O’Connell guest star.

¢ Scheduled on two hours of “20/20” (8 p.m., ABC): “Grey’s Anatomy”; myths and lies.

¢ Five possible bird flu victims wash up on a beach on “Numb3rs” (9 p.m., CBS).