John McCain already tried that.


The “Today” show has recruited the former Alaska governor Sarah Palin to be a guest co-host on Tuesday. NBC wants Ms. Palin to be a channel changer in the same way Senator McCain’s 2008 presidential campaign hoped Ms. Palin would be a game changer. Back then Senator McCain was worried about Barack Obama. “Today” fears Katie Couric, an alumna who is about to start her own syndicated show and on Monday began a weeklong star turn as a guest host on ABC’s “Good Morning America,” alongside George Stephanopoulos.


“Today” has held the No. 1 spot in the weekly ratings for 16 years straight, but ABC is narrowing the gap. NBC was apparently so unnerved by Ms. Couric’s appearance on the rival morning show that the network jumped the gun, persuading Ms. Palin to give a phone interview from Minnesota on Monday, even though her gig as a guest host was not until Tuesday. The promotions made it seem as if Ms. Palin were already on the set.


Ms. Palin, who never misses a chance to poke at what she calls “the liberal media,” said in the interview, “I appreciate NBC’s boldness in having me on, and, you know, doesn’t it kind of reflect the diversity of opinion that I hear that you all espouse?”


Meredith Vieira added dryly, “Or desperation.”


Her colleagues laughed knowingly.


Ms. Vieira, who quit her job as co-host of “Today” in June, was also brought in Monday as a surprise guest host. Ryan Seacrest is expected to appear on Tuesday.


Morning shows always compete, but usually it’s over guests, not hosts. Now contracts are up, change is in the air, and that means viewers have a front-row seat to the discomfort of hosts whose jobs may be on the line.


Monday’s display was more savage than a ratings contest or a booking war; at times it looked as intimate and creepily intrusive as the elimination rounds of a particularly cutthroat reality show. It’s been a long time since NBC put Deborah Norville on the couch alongside Jane Pauley and Bryant Gumbel and turned “Today” into a morning show version of “All About Eve.”


These days it is Ann Curry, who inherited Ms. Vieira’s place but not her popularity, who looks vulnerable.


Ms. Curry had to sit, silent and smiling, on the “Today” set on Monday, alongside Matt Lauer as he urged Ms. Vieira to announce that she would help cover the 2012 summer Olympics and be his co-host, with Bob Costas, for the opening ceremony of the London games. (He did not say what role Ms. Curry would play, if any.)


Earlier, when Mr. Lauer began announcing that Ms. Palin would be a guest host, Ms. Curry smiled grimly, then looked down at her desk, patting papers.


ABC at least had the grace to let Robin Roberts take a vacation and be off the “Good Morning America” set when Ms. Couric took her place.


And that was merciful, because Ms. Roberts, however hard she tries, is no match for that former “Today” host. Neither, really, was Ms. Vieira.


NBC promoted Monday’s show by promising the return of a former “Today” show legend, and asking viewers to guess which one. Ms. Vieira is a popular television personality, but mostly the publicity stunt made NBC look desperate. Ms. Couric, the real “Today” show legend, was on ABC, beaming as she shared a desk with Mr. Stephanopoulos and took a twirl with one of the dancers from “Dancing With the Stars.”


The atmosphere on “Good Morning America” couldn’t have been more cheerful and energetic: Ms. Couric and the rest of the show’s co-hosts were as giddy and upbeat as a winning team preparing for its reward on “The Apprentice.” The “Today” hosts looked a lot like a losing team putting on a game face en route to Donald Trump’s boardroom. Ms. Couric made a point of rubbing it in, sending out a tweet that showed her posing impishly next to a wax likeness of Mr. Lauer alongside a “Good Morning America” news anchor, Josh Elliott.


“CBS This Morning,” meanwhile, still a distant third despite a makeover that included bringing on Charlie Rose and Gayle King as co-hosts, made a stab by inviting Oprah Winfrey on Monday. And that was awkwardly personal too: It looked as if Ms. King were trying to help her best friend, Ms. Winfrey, by giving her a platform to dismiss news reports that her cable network, OWN, is a flop, but it’s more likely that Ms. Winfrey wanted to use her star power to improve Ms. King’s ratings.


“I think this is the right combination,” she assured Ms. King and Mr. Rose. “I think CBS has finally gotten it right.” Ms. Winfrey’s praise for her friend was so effusive that Ms. King had to intervene, saying, “This is boring.”


It wasn’t boring, exactly. Mostly, the morning shows on Monday were disturbingly close to the skin.