NEW YORK—After six years at the helm of global public relations giant Burson-Marsteller, chief executive Mark Penn is leaving the firm to take a new senior strategy role at longtime client Microsoft.

His position as global chief executive at Burson will be taken over by former Clinton White House aide Don Baer, who became worldwide vice chairman of Burson-Marsteller in 2008.

Penn will be corporate vice president of strategic and special projects for Microsoft, reporting to Steve Ballmer and working with what he describes as “an interdisciplinary SWAT team” in both Washington, DC, and Redmond, Wash., drawing on his own expertise in research and communications and working with a variety of other disciplines to help issues critical to the company and its stakeholders. He will not be involved in policy issues, the company says.

“Mark has an incredible background in research, demographics, marketing and positioning and a proven history in developing unique insights that drive success,” Ballmer says. “With a strong set of products and an exciting pipeline for the next year, Mark’s experience and out-of-the-box thinking will help us more effectively reach new consumers and grow market share.”  

Penn has served as a personal advisor to Microsoft founder and former CEO Bill Gates, and has been a key adviser to senior leadership at the software giant since 1998. He helped Microsoft rebuild its reputation in the wake of its bruising anti-trust battle to establish itself as a “Most Trusted Company,” according to The Wall Street Journal.

“In many ways, this will be an extension of the work I have been doing with Microsoft over the past 14 years, except that I will be doing it from inside the company with the kind of full access that comes with an in-house role,” says Penn. “I have always been interested in helping companies address the big challenges, and because of its broad range of products and its broad spectrum of innovation, Microsoft is in the forefront on a lot of those challenges.”

The move comes just weeks after a Vanity Fair article about the “lost decade of Microsoft,” in which report Kurt Eichenwald suggested that a series “astonishingly foolish management decisions… could serve as a business-school case study on the pitfalls of success.”

Penn, who founded the Washington, DC-based research company Penn Schoen Berland and has played a significant role in Washington politics, primarily as a campaign advisor to both Bill and Hilary Clinton, was named chief executive of the WPP-owned agency at the end of 2006—after a five-year period during which the firm went through three CEOs and saw fee income decline to around $250 million.

Under his leadership, Burson has staged an impressive recovery, being named North American Agency of the Year by this publication last year, and is expected to hit around $480 million in fee income in 2012.

WPP chief executive Martin Sorrell told the Holmes Report that the firm had performed well under Penn’s leadership and that he expected that to continue under Baer. “Burson is in good shape and Don will continue to focus on digital, and integration, and global, and strategy. He has good people skills—he is very collegial—and good client counseling skills.”

Penn's tenure was not without controversy, including criticisms of his people management skills. There was also negative publicity regarding his role in the Hillary Clinton campaign, including a conflict that resulted in the Colombian government pulling its business from Burson. The firm was accused of a smear campaign against Google in its work for Facebook.

Penn’s other clients include corporate leaders such as Sir Howard Stringer and Bill Ford; political leaders including UK Prime Minister Tony Blair, Israeli Prime Minister Menachem Begin, and Venezuelan President Luis Herrera Campins; and companies including Ford, Merck, BP, Sony, and McDonald’s.

He is the author of the 2007 book “Microtrends,” a look at small forces behind tomorrow’s big changes.

“It is going to be difficult to say goodbye to all the firms I have had a hand in running,” Penn says. “Burson-Marsteller has been through a great transformation over the past six years. We have brought in new talent and brought along the next generation of talent from within the firm, and we have a very strong senior leadership team in place in North America and around the globe. Don is someone I have worked with since the Clinton White House, we have worked closely together over the past five years, and I know he is going to be a hands-on, working CEO in the same way that I have been.”

Prior to Burson, Baer helped lead global media company Discovery Communications as senior executive vice president for strategy and development and an executive committee member, reporting to the CEO. Earlier, he was a senior adviser to President Bill Clinton as an assistant to the President and White House director of strategic planning and communications and, before, as chief speechwriter/director of speechwriting and research.

Before that, Baer was a journalist at US News & World Report and The American Lawyer and a media lawyer at New York’s Patterson Belknap Webb & Tyler.

Baer says that he intends to continue Burson’s commitment to its evidence-based approach, having also served as chairman of PSB. “The insights that we draw from Penn Schoen Berland’s research drive everything we do, and it is absolutely critical that the integration between the two firms should continue,” he says.

“I am inheriting a firm that is as strong as it has ever been, but at the same time there is room for great growth. This is a time of dynamic change in our field, and we have an opportunity to be the most creative, idea-driven, results-oriented firm in the world.”