The rare cases of a woman being sponsored for the top slot by a powerful male tend to stick in one's mind.

Indra Nooyi, chosen in 2007 by PepsiCo Chief Executive Officer Steven Reinemund to succeed him as CEO. At the time, Nooyi wasn't considered the top candidate, but Reinemund saw her as the right person to lead the company into a more sustainable future.

Sarah Palin — picked by John McCain as his running mate on the Republican ticket in 2008. An unknown governor from a faraway state, Palin wasn't on anyone's radar, but McCain saw her as jump-starting his lacklustre campaign with refreshing heartland energy.

Whether one agrees with Nooyi's vision for PepsiCo or Palin's vision for the Republican Party, one thing is for sure: Neither would be the notables they are without powerful sponsors. Unfortunately, most women don't get similar backing, and they pay a huge price. Here are the facts:

In spite of their progress on the lower and middle rungs of the career ladder, women aren't making it to the top. In the US, women hold only 15 per cent seats on boards, account for less than 5 per cent of top earners and make up a mere 3 per cent of Fortune 500 CEOs. Those last slippery rungs are extraordinarily difficult for women to climb. To be sure, at the most senior levels the competition is fierce and many men and women fail. But men reach the top in much more impressive numbers. Why?

Lack of push

A new study from the Centre for Work-Life Policy sheds new light on this question. Women who are top performers stall out not for lack of drive, but for lack of push. They simply don't have the powerful backing needed to prepare them, propel them and protect them through the perilous straits of senior management.

In a word, women lack sponsors. While executive women have tonnes of mentors dispensing friendly advice, they're half as likely as executive men to have a sponsor.

What's a sponsor? A sponsor is a powerful executive in the direct line of command who uses up chips on behalf of a protege and advocates for the next promotion. They provide introductions to key clients and customers, promote visibility with corporate bigwigs, and open the door to power. The data show that this high-octane help boosts prospects for advancement by 23 per cent for men and 19 per cent for women.

Sounds straightforward. Yet women have difficulty developing these powerful relationships. The new research uncovers some serious tripwires.

The first is that high-performing women frequently underestimate the pivotal role that relationships play in advancement, choosing to believe hard work and bottom-line results will net them their due reward. Many feel that getting ahead based on who you know is an unfair, even dirty, tactic. This belief in meritocracy persists, even as they're passed over for a plum assignment, a pay raise or a promotion.

The study also shows that women's reluctance to seek out senior male sponsors may be amply justified. The typical sponsorship relationship — an older, married man spending one-on-one time, sometimes off-site and after-hours, with a younger, often-unmarried woman — can look a lot like an affair.

The greater the power disparity between the male and the female, the more intense the speculation becomes that the relationship is more than professional — with potential penalties for both. If the woman is subsequently promoted, her achievement may be undermined by office gossip. Nor does the senior man walk away scot-free. If it looks like he spent too much time with the junior woman, he incurs the risk of a sexual harassment suit or even dismissal.

Cultivate contact

The data in the new study are sobering: Fear of being suspected of a sexual liaison causes 64 per cent of senior male executives to avoid one-on-one contact with junior women; for the same reason, 50 per cent of junior women hesitate to initiate or cultivate such contact with a male superior.

The good news is that the word on sponsorship is out: New York-based research group Catalyst, as well as the CWLP, has a new study that highlights the critical importance of sponsors and a sizable group of corporate heavy-hitters, including American Express, Deloitte, Morgan Stanley and Intel are experimenting with initiatives that make sponsorship much more available to high-performing women.