Johnson & Johnson’s Sheri McCoy has been rocketing up Fortune‘s Most Powerful Women list. This year, she is No. 12, vs. No. 44 in 2008.

The giant leap was the result of her promotion to worldwide chairman of J&J’s pharmaceuticals group, a $22.5 billion-a year business. And Fortune has been predicting for a while that McCoy has a good shot to be J&J’s next CEO.

Sure enough, McCoy is now ascending to vice chairman and expanding her portfolio to include J&J’s consumer group, the company’s office of science and technology, and corporate affairs. J&J yesterday announced her promotion, along with that of Alex Gorsky, worldwide chairman of the company’s medical device and diagnostics group.

So it looks to be a bake-off between Gorsky, 50, and McCoy, 52, to replace 62-year-old Bill Weldon as CEO. J&J’s consumer business will be McCoy’s key test as a turnaround executive. The unit includes McNeil Consumer Healthcare, lately roiled by quality-control problems and recalls of mega-brands like Tylenol and Rolaids.

As Fortune detailed in August, McNeil’s torrent of trouble has damaged the reputation of one of the world’s most trusted companies and also led to the fall of J&J’s other star woman exec, Colleen Goggins, who headed the consumer group.

The contrast between Goggins and McCoy is striking. While Goggins was a renowned micromanager and not very popular with J&J’s troops, McCoy is one of J&J’s most well-liked executives. She’s known for having an open and warm style. A mother of three boys, she has eagerly shared her own experience of juggling a high-powered career and family and worked to set an example for other women managers.

A chemical engineer by training, McCoy started at J&J in 1982 as an associate scientist in R&D. She later moved into marketing and then ran baby products, wound care, and surgical care.

McCoy’s ascent, wherever it leads, shows that success requires not just juggling but flexibility too. Rising to the top is rarely a straight line.