This is who Madison Avenue wants to replace Costolo as Twitter CEO

Investors in Twitter are currently wondering out-loud whether it might be time for a leadership change at the company, following its lackluster financial performance in the last quarter and weak guidance for the rest of the year.

Were Twitter CEO Dick Costolo to leave, or be forced to leave, insiders have singled out the company's revenue boss Adam Bain as the most logical replacement.

And those outside the company who work with 40-year-old Bain - Twitter's advertisers - would be thrilled to have him at the top too.

We spoke to a bunch of people from across the advertising community about Bain's suitability as a successor to Costolo, and, without fail, everyone we spoke to sung his praises. They were gushing.

As one senior advertising agency exec who asked not to be named told Business Insider: "He's a shrewd guy. Very cool-headed. Nice to work with. Very smart. And very well-regarded by the industry; people really warm to him, so he'd be the obvious choice."

Bain's achievements so far

The first argument that came up in opposition the idea of Bain taking over as Twitter CEO among the people we spoke to is that, as a sales guy, he lacks product chops. But his CV tells a different story.

Bain joined Twitter back in 2010 from Fox, where he was president of its audience network (FAN,) an ad platform that helped monetize News Corporation's web properties and many hundreds of third-party websites.

Prior to that he was Fox Interactive Media's first chief technology officer, helping lead several high-profile acquisitions such as MySpace, Photobucket, IGN, and Scout Media.

And when he first started at News Corp back in the late 1990s/early 2000s, Bain was responsible for running the technology and product divisions at FOXSports.com.

Even at Twitter, while his role has been ostensibly sales and partnerships focused, he has helped build out advertising products.

The success of Twitter Amplify can be largely attributed to Bain. Twitter Amplify allows broadcasters to extend real-time photos or videos into Twitter ads, which can be sponsored by a brand. Its 80+ partners so far include NFL, McDonald's, Verizon, CBS, American Express, Fox TV, BBC Global News, Sky, and Viacom.

Marketers have found "strengths and limitations" to Amplify so far, but Brian Wieser, senior analyst at Pivotal Research Group, told AdAge in 2014that Amplify had crucially "given Twitter a seat at the table with senior marketers that it otherwise might not have."

Arguably, Bain's greatest achievement to date is growing the company to a solid enough commercial position for the company to IPO in 2013. And while Twitter's revenue and guidance isn't where investors and analysts think it should be at the moment, it is still growing in double digit percentages.

Support for Bain internally

Twitter's IPO created 1,600 new millionaires, mostly from rank-and-file employees, according to data from market research analyst PrivCo. That no doubt puts Bain, and others who steered the company through the IPO process (which includes Dick Costolo), in a solid position internally.

Were Costolo to leave Bain is likely to be a popular choice among staff. We stress here that this is merely hypothetical right now. Many people we spoke to said that those calling for Costolo to exit are likely to be short-termist investors who don't understand the company; Costolo himself says he has the full confidence of the board; and the eight-person board is made up of Costolo himself, alongside Twitter's co-founders and former CEOs Evan Williams and Jack Dorsey. Williams and Dorsey both understand how difficult a job it is to be Twitter's CEO.

One source who has worked closely with Twitter for years said of Bain: "He's grown with the business, and has a great feel for the culture, the place, and the people."

That said, those that have also been there since the early days may wonder whether the installation of Bain at the top would signal a move away from its entrepreneurial spirit of old. Even some of the advertising execs we spoke to said this could be a barrier to his promotion.

One source close to Twitter said that while Bain has been "widely viewed as the guy who has done the best at Twitter," the only evidence of his success so far is on the revenue side. But Twitter's problem (that its own chief financial officer admits to being its problem) is that while nearly everybody in the world knows what Twitter is, just a small subset of people - journalists, famous people - know how to use it. The product is complicated and it needs a shakeup, or a move in a different direction, our source said, adding that Bain probably isn't the right person to do that.

An advertising agency source suggested Bain could potentially allay product concerns by bringing on board a right-hand man - kind of like the opposite of what product visionary Mark Zuckerberg did when he appointed Sheryl Sandberg as Facebook's COO - or elevating someone in the internal product team such as SVP of product Kevin Weil to a more senior role.

The investor's choice

Pivotal's Wieser told Business Insider that the single biggest challenge between Twitter and Wall Street is "communicating a consistent message about what investors should focus on." Wieser said he was "surprised" after Twitter's IPO roadshow that the company chose to talk about the user story, rather than the "wonderful commercial story" he believes the company should have focused on instead.

One person close to the company told Business Insider senior editor Alexei Oreskovic that Twitter's November analyst day showed Bain "is the most effective communicator at the company."

Soon Twitter is going to have a far richer commercial story it will need to communicate: Twitter has opened up some of its ad inventory to Google it recently acquired marketing company TellApart that should help it give marketers more granular information about how effective their campaigns are; and we're still waiting to hear more about what kind of impact Twitter's $350 million acquisition of mobile ad server MoPub has had on the business.

These are all solid advertising-based stories for Twitter to shout about - long-term revenue opportunities that are not entirely directly linked with user growth (which is stalling and the main concern about Twitter with investors.)

But perhaps this also points to the idea that, as Wieser suggests, Twitter needs to make a decision on what it wants to be and how it wants to present itself to the outside world, before it makes a decision on who should be its CEO.