The Democratic National Convention opens tonight in Boston. Television viewers and political junkies can watch as much or as little of it as they want. The big three networks, ABC, CBS and NBC, have cut down coverage to one hour per night, beginning at 9 p.m. CDT. And Tuesday night, there is no network coverage at all.

Cable news will fill this vacuum with more comprehensive coverage. CNN has even given the convention its own title and will offer three hours of coverage through Thursday on “America Votes 2004: The Democratic National Convention” (7 p.m.) with hosts Wolf Blitzer, Aaron Brown, Jeff Greenfield, Larry King, Bill Schneider and Judy Woodruff. Both MSNBC and Fox News will cover the convention through their regularly scheduled lineup of news and talk shows. Jim Lehrer anchors three hours of PBS coverage (7 p.m.). Viewers in search of a more direct feed can tune in to C-SPAN at 3 p.m.

• Ken Scott stars in “Messiah” (8 p.m., BBC America), a smart if blood-splattered psychological thriller that concludes next Monday. He’s London detective Red Metcalfe, a cop so straight he once turned in his own brother for murder. Haunted by that sibling betrayal, he turns his attention to climbing inside the psyches of serial killers.

But even Red seems baffled by a grisly parade of corpses, each dispatched in a horrible fashion and found with their tongues removed and a silver spoon shoved in their mouths. Not for the squeamish, “Messiah” should appeal to fans of “Seven” and “Silence of the Lambs.” It’s filled with clever, offbeat plot devices and character tics, as when Red returns home to discuss his agonies with his deaf wife, who grows increasingly upset with his emotional reticence.

Tonight’s other highlights

• Ray can’t tell whether Michael is sick or playing hooky on “Everybody Loves Raymond” (7 p.m., CBS).
• Two wives swap lives on “Trading Spouses: Meet Your New Wife” (7 p.m., Fox).
• A robber leaves two dead as one victim clings to life on “CSI: Miami” (8 p.m., CBS).
• A former “Suddenly Susan” star offers a brutally funny take on her place in the celebrity food chain on the repeat comedy special “Kathy Griffin: The D-List” (9 p.m., Bravo).

Late night

The U.S. Olympic synchronized swimming team performs on “Late Show with David Letterman” (10:35 p.m., CBS).