That, and other news, in today’s Political Panorama.

A new ABC News/Washington Post poll shows a big Barack Obama lead and the result of John McCain’s attacks over the past week: A drop in his favorability ratings. Today marks a reboot to a gentler campaign, so what will be interesting is how he uses a planned appearance on “Late Show with David Letterman” on Thursday to enhance his image.  Letterman has been relentless after McCain cancelled a planned appearance at the last minute to attend to the financial crisis in Washington, only to appear  cross town on “CBS Evening News with Katie Couric.” I would expect an effort by McCain to simply be a bit more irreverent, to try to soften his image from the debates, and to make light of some of his campaign’s past foibles. Remember that Hillary Clinton made the best use of late-night TV, diffusing otherwise embarrassing episodes with humor. Before the Pennsylvania primary, she joked about sniper fire, a reference to the flap over her apparently embellishment of the dangers in a 1996 trip to Kosovo.

The same may be true of Sarah Palin if she ends up doing a cameo on “Saturday Night Live,” although it will be a bit awkward if she meets face to face with Tina Fey. Fey told TV Guide this week, “If she wins, I’m done. I can’t do that for four years. And by ‘I’m done,’ I mean I’m leaving Earth.”

The Bus to Nowhere: Howard Kurtz of the Washington Post writes that the Boys on the Bus may be a journalistic dinosaur. “Does the campaign trail still matter much in an age of digital warfare? Or is it now a mere sideshow, meant to provide the media with pretty pictures of colorful crowds while the guts of the contest unfold elsewhere? And if so, are the boys (and girls) on the bus spinning their wheels?

“”Anything interesting that happens on the road is going to be eaten up before you can get to it,” says Slate correspondent John Dickerson. “By the time you see the papers, you feel like you know it all.””

Tell It to the King: Guests on “Larry King Live” this evening: Dean Cain, a McCain supporter, and Sheryl Crow, an Obama supporter.

Keaton Concern: Preservation advocate Diane Keaton mourns the loss of the Ambassador Hotel and argues the environmental case for saving historic structures.

A Return to the War Room: Chris Hegedus and D.A. Pennebaker update their 1992 campaign documentary with a Sundance doc.