Well, this could be interesting. The Arizona Republican Presidential Debate (6 p.m., CNN) is the first since Rick Santorum took the lead in some national polls over his GOP rivals, and it's the last before the Arizona and Michigan primaries on Tuesday and the Super Tuesday primaries in March.
Santorum will be joined by Mitt Romney, Newt Gingrich and Ron Paul. CNN's Jon King will moderate the two-hour program.
Elsewhere on TV ...
Survivor: One World (7 p.m., CBS/Ch. 2): The women are desperate for a win. And the outcasts join together under an unlikely leader.
The Middle (7 p.m., ABC/Ch. 4): The kids call a family meeting to complain about their parents.
Whitney (7 p.m., NBC/Ch. 5): Whitney tries to act sexy for Alex.
Nature (7 p.m., PBS/Ch. 7): Why size matters in the world of whales.
American Idol (7 p.m., Fox/Ch. 13): The first group of semifinalists is announced.
One Tree Hill (7 p.m., CW/Ch. 30): Chad Michael Murray returns as Lucas as this shows winds down toward its conclusion.
NBA (7 p.m., ROOT): Utah Jazz at Minnesota Timberwolves
Suburgatory (7:30 p.m., ABC/Ch. 4): Dalia tries to get back at Tessa by making friends with Lisa.
Criminal Minds (8 p.m., CBS/Ch. 2): The team investigates a string of brutal home invasions.
Modern Family (8 p.m., ABC/Ch. 4): Gloria accidentally discovers Claire's secret.
Rock Center with Brian Williams (8 p.m., NBC/Ch. 5): With a rising demand for rhino horn, ranchers and game wardens are trying to save the animals.
Happy Endings (8:30 p.m., ABC/Ch. 4): Brad and Jane have their annual argument.
CSI (9 p.m., CBS/Ch. 2): An entire house is stolen right off its foundation.
20/20 (9 p.m., ABC/Ch. 4): In a "Before They Were Famous" episode, Robin Roberts looks at Oscar nominees - you guessed it! - before they were famous.
Law & Order: SVU (9 p.m., NBC/Ch. 5): A series of escorts goes missing.
Top Chef: Texas (11 p.m., Bravo): The final three contestants have to create a dish with the them of fire and ice.
Royal Pains (11 p.m., USA): Hank struggles to cope with Jack's illness.
