Brian Williams still has a lot of explaining to do. His replacement, Lester Holt, has big shoes to fill. But the way both men perform over the next few months is unlikely to immediately affect the relationship between “NBC Nightly News” and its advertisers. With the lion's share of ad inventory already sold at upfronts, most of it to deep-pocketed pharmaceutical and self-care advertisers that have been guaranteed to reach a certain minimum number of viewers (and are attracted to network news' old, loyal audiences), it makes no difference whether Holt succeeds or fails. 

“Most news buys are done in the long-term marketplace, so there are guarantees,” Omnicom president of national broadcast Chris Geraci said. “While fluctuations aren't good, you know you're going to get a certain number of people and the network is responsible." NBC did not reply to requests for comment about its relationships with advertisers. 

Network newscasts are a peculiar fixture in the television advertising universe - the format whose golden age came and went nearly 60 years ago now finds itself in a persistent decline, and the percentage of American adults watching network newscasts has fallen by nearly half since 1980, according to the Pew Research Center. During that time, the percentage of young people (i.e. those aged 18-29) watching TV news has slid precipitously, from 49 percent in 2006 to 34 percent in 2012.

Yet the number of people tuning in to network evening news is still nearly three times larger than the daily circulation of “USA Today,” and nearly four times larger than the combined number of viewers tuning in to primetime programming on cable competitors Fox News Channel, MSNBC and CNN. “It's still as close as you can get to a mass scale,” said Amy Mitchell, Pew's director of journalism research.

Loyalty among older Americans is the only reason network nightly news ratings haven’t fallen off a cliff. While the median age among TV viewers in general is going up – their median age is 44 years old, according to research conducted by Moffett Nathanson – TV news's viewer base is especially old. Seventy-three percent of American adults aged 65 or older watch news on TV, compared to just 34 percent of Americans aged 18 to 29.   

“That's why you see pharmaceuticals advertised and almost nothing else,” Geraci said. “News in general, because it skews older, is an efficient way to reach that older audience. It is one of the few advertising categories that is consistently aimed at that demographic.”

The sheer amount of inventory, or ads available for advertisers to purchase, also makes news an attractive vehicle for deep-pocketed advertisers. Unlike a sexy prime-time drama that may only air a dozen episodes before it disappears for the season, network news programs like NBC Nightly News broadcast every night. “You use it more as a sustaining, support sort of vehicle,” Geraci said. “You'll have continuity in your news buy that you may not have in other places.”

Those same advertisers will often spread their dollars around among all three networks. Brands like Cialis and Aleve, for example, have been among the top spending advertisers on both CBS and NBC's evening newscasts this past year. The top three shows in terms of dollars spent for Dr. Scholls were NBC, ABC and CBS's eveng newscasts. "It’s safe to say pharmaceuticals are spreading themselves across those shows," said Jason Damata, spokesperson for "You see a lot of the same brands." 

In suspending Williams rather than firing him, the network may be holding out hope that the anchor might eventually be able to rehabilitate his image. That process can take a while - as long as six years, according to according to Q Scores Company executive vice president Henry Schafer. “I wouldn't say it's totally impossible,” Schafer said. “It's just a matter of what kinds of steps are taken.” 

But no matter how long NBC decides to hold onto Williams after his six-month suspension ends, "Nightly News" will continue to draw interest from pharma advertisers because it can deliver a guaranteed audience. “They're on the hook, for the most part,” Geraci said.