Democratic National Convention coverage (5 p.m., CNN; 6 p.m., MSNBC; 7 p.m., PBS; 8:45 p.m., Fox News; 9 p.m., ABC, CBS, NBC, BET) concludes with candidate Barack Obama’s acceptance speech.

If history is any guide, this should draw a large combined audience for the networks covering the convention.

In 2004, the acceptance speeches for Sen. John Kerry and President George W. Bush were each viewed by more than 25 million viewers.

On nights like this, when so many eyeballs are glued to an event with the potential to make history, it’s always interesting to note what nonparticipating networks are airing.

Are they counterprogramming or offering commentary on the event? Sometimes they seem to be doing a little bit of both.

Wouldn’t it be cheeky for Fox, the sister network of the right-wing Fox News Network, to air “The Moment of Truth” (7 p.m., Fox) right before the big speech?

On the other hand, MSNBC has set itself up in prime time as the pro-Democrat anti-Fox network, and its sister network, CNBC, is airing “Deal or No Deal” (8 p.m., CNBC), so perhaps the search for editorial commentary is a bit of a stretch.

Given the circumstances, the titles of some of tonight’s cable movies seem to take on grave and fateful overtones. There’s the 1993 thriller “Point of No Return” (7 p.m., Ion) and the 1997 Bond adventure “Tomorrow Never Dies” (7 p.m., AMC).

Others, like the 1958 Western “The Big Country” (7 p.m., TCM), seem more in tune with lofty oratory.

Given the historic occasion of a black man accepting his party’s nomination for president, some of the alternative choices seem awkward at very best.

WE airs the 1985 epic “The Color Purple” (7 p.m., WE), and TV Land presents back-to-back repeats of “The Cosby Show” (7 p.m. and 7:30 p.m.) and “Sandford and Son” (8 p.m. and 8:30 p.m.). IFC gets the bad-taste award for airing the 2002 thriller “Assassination Tango” (8 p.m., IFC) opposite the big event.

And viewers who look at the event with a skeptical eye may have to settle for a repeat of “Mythbusters” (9 p.m., Discovery).

¢ Columbus may have sailed the ocean blue in 1492, but he was hardly the first. The “Naked Science” (9 p.m., National Geographic) special “First to Cross the Ocean” looks at ancient sea crossings, the migrations that changed the fates of continents.

Employing DNA testing and other advanced techniques, scientists theorize that Africans may have sailed to Australia more than 50,000 years ago.

¢ “The Works” (9 p.m., History) looks at the history and the future of the motorcycle, from its origins as a steam-powered vehicle to experiments in hybrid technology.

Tonight’s other highlights

Note: Local listings may vary because of preseason NFL coverage.

¢ The Redskins host the Jaguars in preseason NFL football action (6 p.m., NBC).

¢ Tennis action at the U.S. Open (6 p.m., USA).

¢ Renee is jealous of Betty on “Ugly Betty” (7 p.m., ABC).

¢ A washed-up boxer expires under seedy circumstances on “CSI” (8 p.m., CBS).