Politics meets reality television as Delaware Sen. Joseph Biden and Alaska Gov. Sarah Palin meet in the vice presidential debate (8 p.m., CBS, NBC, ABC, Fox, PBS, CNN, Fox News, MSNBC, BBC America, Telemundo).

After months of primaries and dozens of debates, the candidates have become familiar faces. Had Sen. John McCain chosen Mitt Romney, Joe Lieberman or Tim Pawlenty as his running mate, tonight’s debate would be just another political event. Does anyone remember anything memorable or quotable about the last presidential debate? I didn’t think so.

Like any popular reality-TV star, Palin arrived on the scene completely unknown and with a strong personality that evoked very different reactions in people.

Not since Richard Nixon picked Spiro Agnew in 1968 has a controversial vice president or potential vice president become a pop-culture icon, complete with merchandise tie-ins. According to People magazine, Palin’s choice of eyewear has caused a stampede to the vision centers. She has even inspired an action-figure doll. Back in the day, the Agnew watch became an instant collectible.

To her supporters, Palin is a tough, sassy and even sexy every-mom – Margaret Thatcher meets Sally Field. To her detractors, she’s Tonya Harding, a tenacious competitor with more than a whiff of menace.

But under the not-so-tough scrutiny of Katie Couric on “The CBS Evening News,” Palin floundered like Kellie Pickler on “Are You Smarter Than a Fifth Grader?” Her command of facts, policy and even basic English grammar seemed to escape her for moments at a time, inspiring a few conservative writers and former supporters to use the word “cringe” in their columns.

Which Palin will emerge in tonight’s 90-minute debate? The confident convention edition or the Couric catastrophe? Her performance has to be seen as a high-wire act worthy of sports or reality spectacle that people will certainly be talking about in the days to come. Will she be an “America Idol” or “The Biggest Loser”? “The Weakest Link” or a “Survivor”? By any measure, this political season has been an “Amazing Race.”

¢ Everybody’s favorite fixture of “Project Runway” returns for a second season of “Tim Gunn’s Guide to Style” (10 p.m., Bravo). This year, he has a new sidekick, Gretta Monahan, who replaces Veronica Webb, who, as I recall, was a bit of a dud.

Every week of “Style” features a style-challenged young woman who turns to Gunn for tough love and counseling. Gunn does a good job of laying out fashion do’s and don’ts and shares ideas about 10 basic items that no woman’s closet should be without.

Tonight’s other highlights

¢ Divisional series Major League playoff games (5:30 p.m. and 9 p.m., approximate, TBS).

¢ Jeff Probst hosts “Survivor” (7 p.m., CBS).

¢ On two episodes of “My Name is Earl” (NBC), Joy quarantined (7 p.m.), Jerry Van Dyke guest stars as an RV owner on Earl’s list (7:30 p.m.).

¢ Wilhelmina offers Betty a job on “Ugly Betty” (7 p.m., ABC).

¢ An “Idol” star and Oscar winner performs on “Jennifer Hudson: In the Spotlight” (9 p.m., BET).

¢ On two episodes of “It’s Always Sunny in Philadelphia” (FX), Mac and Charlie go underground (9 p.m.), and the gang reacts (9:30 p.m.).