Kate Renwick-Espinosa was weeks into a four-month maternity leave from VSP Vision Care when her boss called and asked to stop by.  He brought news that Renwick-Espinosa was being offered a promotion to vice president of marketing of parent company VSP Global.

Renwick-Espinosa had known the company’s marketing was expanding, but she didn’t know the new position had been created, and she certainly had no idea she would be tapped for it while out on leave.

She credits largely the support and advocacy of higher-ups who vouched for her credibility and pressed for her promotion. “I think I was provided with that opportunity because I had good sponsors, people who had been investing in my development,” she says.

Now the chief marketing officer of VSP Global in Rancho Cordova, Renwick-Espinosa’s experience highlights the impact so-called sponsors can have on women’s professional ascent. For years, as organizations have questioned why more women weren’t reaching top echelons, a lack of mentoring became the answer. In response, companies rolled out extensive mentoring programs. Yet women’s progress still stalled, prompting new research as to why.

If workplace mentoring doesn’t help women advance to senior levels, what does? A different type of professional relationship, it turns out. Sponsorship.

“The definition for me of a mentor is someone who is going to work with you to show you the ropes, talk about best practices and provide tips and techniques from their personal experiences,” says Wendy Beecham, managing director of executive education at the UC Davis Graduate School of Management. “A sponsor is someone who can advocate for an opportunity for you.”

While mentors may sometimes end up being sponsors if they are placed high enough within organizations, it’s important to understand the difference between the two. Mentors tend to focus more on the traditional role of support and advice, while sponsors focus specifically on advancement. Following numerous studies, it has been widely recognized that companies that understand this distinction can better encourage women to advance to senior positions.

Consider the research from Catalyst Inc., an advisory organization working to advance women in business. In its 2008 survey of thousands of male and female MBA graduates, Catalyst found that women are actually mentored more than men. Yet, in a follow-up study, the company discovered that of those employees with mentors, 72 percent of men had been promoted two years later, compared with only 65 percent of women.

Men’s mentors, the research revealed, tended to be more highly placed within organizations and more likely in a position to influence promotions.

While increased sponsorship of women is no silver bullet to closing the gender gap, it is considered a vital part of addressing the issue.

“Done well, sponsorship can serve as a highly effective intervention to accelerate women’s career velocity. Lack of sponsorship is one indicator of what’s really been holding many women back — exclusion from organizations’ most influential networks. Sponsorship can finesse access to these powerful networks, providing impressive benefits to leaders, high-performing employees and organizations themselves,” states a 2011 Catalyst report.

That was certainly the case with Beecham. In the late 1990s, she served as the vice president of content development for West, a Thomson Reuters publishing company, and was responsible for licensing and database development within its legal library. That meant Beecham spent her time negotiating significant licensing deals, many of which required senior management approval.

As a result, she garnered a lot of face time with senior executives. Her skills were well known by higher-ups since she had established credibility through interaction. So when a C-level position opened at a Thomson company in London, Beecham was invited to apply.

“The head of my division advocated for me to be considered for that role, even though I’d never had a CEO role before,” Beecham says. “Because of my credibility and my experience, they took a chance on me. I never would have been considered for that role had he not advocated for me.”

She was ultimately offered the job, and for four years Beecham served as managing director of Sweet & Maxwell, a legal publishing company in London.

“Getting into the C-suite role is much more difficult without advocacy,” Beecham says.

Advocacy — or sponsorship — plays a role in promotions and hiring in positions below the C-suite, too. Whether the sponsor is a man or woman doesn’t matter; what matters is influence.

For Laura Costa, now COO of VSP Vision Care, that person was a superior. Costa, who had been serving as director of customer service, saw her responsibilities grow rapidly as the company expanded. Her boss at the time, a woman named MaryAnn, had a good reputation and considerable influence with management. She noticed that Costa was thriving amid expanding responsibilities, advocated for the creation of a new vice president position and pushed for Costa to fill it.

“She was able to advocate on my behalf to the senior vice president and the president that the scope of the job was large enough and the timing was right for me to have earned the promotion,” Costa says.

Even after Costa became a vice president, MaryAnn continued to serve as a mentor by helping her understand and meet the expectations of the title. By many accounts, the role of sponsor shouldn’t end with the promotion; he or she should also help with a successful transition.

For sponsors, that success is often the reward for their willingness to advocate on someone’s behalf. Ric Steere, now vice president of global business development of VSP Global, first hired Renwick-Espinosa 20 years ago, and he has consistently promoted her value to others.

“Lack of sponsorship is one indicator of what’s really been holding many women back — exclusion from organizations’ most influential networks.”

“Sponsoring Women to Success,” a 2008 Catalyst Inc. report

“It is always good to see good people succeed,” Steere says. “The reward is having a successful organization [and] working with people you enjoy. It is very motivating knowing that you have helped contribute to someone’s success, which contributes to the success of the organization.”

None of this is to say, of course, that mentoring doesn’t have its place in supporting career advancements. For both men and women, mentors can help individuals develop ideas and discuss long-term career goals and strategies for achieving them.

A director of public affairs for Siemens Industry Inc. in Sacramento, Becky Johnson was recently paired with a mentor through the company’s formal mentoring program. Her mentor, based in Washington, D.C., and fairly new to Siemens, comes from the private consulting world. Although that’s a significantly different background than Johnson’s, she wants to learn more about it.

“She’s working on a lot of the types of projects that are of interest to me,” Johnson says. “Her experience is something I hope to learn from. I want to, in the next couple of years, pursue graduate school, and I hope to talk with her about which way she thinks I should go. An MPA? An MBA? Or something specific to infrastructure and planning? This is the perfect type of thing to discuss with a mentor.”

For her part, Johnson is also mentoring a woman who works on the operational side of Siemens. Johnson is helping the woman gain visibility outside her role by inviting her to meetings with leaders of business and government.

“I’m helping connect the dots among various parts of her business,” Johnson says. “It’s important for her to see her role within the organization, to see how critical she is in the big picture.”

While many women find mentors through company programs, some happen more informally. Elisabeth Brinton, SMUD’s chief customer officer, has long sought out mentors on her own. Raised by a successful businesswoman, Brinton grew up surrounded by her mother’s mentors — both men and women — and came to understand them as part of a strategy to grow and succeed, professionally and personally.

Brinton says her mentors, which have ranged from a CEO to corporate counsel to colleagues, have brought perspective, identified weaknesses and taught strategies to overcome barriers.

“I hate to say it, but gender bias is still a reality in this country,” Brinton says. “It still is prevalent. It kind of displays itself in different ways.”

These days, that may include anything from a company assuming a mother is uninterested in an international assignment (says Beecham, “You don’t get to make that choice for her.”), to male leaders unconsciously hiring people like themselves.

Yet, Beecham points out, there is also unconscious bias at work on the side of many women as well. Typically, she says, women tend to assume that if they work hard and excel at their jobs, they’ll be noticed by higher-ups and considered for promotions and plum assignments. Yet, often they don’t voice their goals or interests.

Additionally, men and women tend to network in different ways. “Women tend to network with people they like and feel comfortable with, whereas men tend to network with people who can help them achieve a certain goal,” Beecham says. Ultimately, that can end up hurting women, since they aren’t necessarily making connections with the people who have the influence to help them.

So how do more women go about getting sponsors? While some companies have begun rolling out formal programs, having a sponsor is typically casual, the type of relationship that simply develops based on demonstrated work and face time.

But there are steps women can take to better their odds of having someone advocate on their behalf. Beecham advises women to network more strategically and to find ways to go beyond their normal discipline and work duties. “Doing your job well is a given,” she says. “It’s about how you get noticed outside your own individual area.” That can mean volunteering for special projects, serving on due diligence teams or building a reputation outside the company.

Regardless of the tactic, the goal is the same — create situations wherein your credibility is visible to those who have the power to advocate.

“It’s hard for us to think that someone might advocate for us,” Beecham says, “but it’s a very professional, normal way of doing business, and men do it all the time.”