When Carol Bartz took over as CEO of Yahoo in January of this year, she was handed a huge task: recapture some of Yahoo’s past glory. Most agreed that doing that meant figuring out what to do with Yahoo search.

Plan A: hand off the search business to Microsoft. But signs are mounting that regulators may not let the deal proceed smoothly, if at all. This led Search Engine Watch’s Danny Sullivan to ask a simple question: “what’s Yahoo’s Plan B for search?

And now we may have at least part of the answer: advertising. According to Kara Swisher of AllThingsDigital, Yahoo will “unveil a major marketing campaign to reset advertiser and consumer perception of the long-troubled company” at Advertising Week in New York.

For advertisers, Yahoo is issuing a reminder that it’s still a “powerhouse unlike any others on the Web when it comes to online display advertising“. For consumers, Yahoo is apparently likely to proceed with plans to brand its network as “your home on the Web”. According to some of Swisher’s sources, Yahoo is already spending tens of millions of dollars buying media online and off. One source she quotes says the amount of capital being deployed is “dramatic“.

While I’m not suggesting that Yahoo’s decision to launch an expensive advertising campaign is directly tied to a Plan B for search, everything Yahoo does at this point is inherently related to the company’s search woes. When it comes to getting consumers back on side, the question, of course, is whether Yahoo really has a messaging problem or whether it has a product problem.

The truth of the matter is that the Yahoo network isn’t exactly hurting for traffic; consumers haven’t abandoned Yahoo. The problem is that the most valuable traffic on the consumer internet is search-related and Yahoo isn’t capturing it. If Yahoo is going to market itself to consumers, it doesn’t need to market its portal and network. Consumers are already there. It needs to get consumers searching again.

But can a marketing campaign get consumers to change their perceptions of Yahoo search? While one might point out that Microsoft seems to be having some success with its expensive Bing campaign, there’s a key difference between Yahoo and Microsoft in this regard: Microsoft actually had something new to tell consumers about. Yahoo doesn’t.

And that’s the problem. The markets Yahoo competes in have changed over the years but from a consumer perspective, Yahoo really hasn’t changed. Since it doesn’t have much of anything new of substance to offer consumers, it has to try to convince them that what it does have is good enough. That’s a real challenge. Just ask another major brand that’s trying to do the same — GM.

In my opinion, if Swisher’s sources are right and Yahoo is launching a costly advertising campaign, it will signal that Yahoo’s leaders, including Bartz, may be more worried about Yahoo’s future than they’re letting on. Spending tens of millions (or more) on advertising when you have nothing new to advertise is more likely a sign of desperation than it is a sign of confidence.