Clinton's stumble in the Iowa caucuses in early January -- in which the Obama campaign was credited with out-organizing her -- led to questions about Penn's leadership that have only intensified since.
Campaign aides said Penn was late in letting Clinton showcase a warmer, more human side that some voters hoped to see.
Aides also have also complained about Penn's unilateral style. After Clinton's defeat in South Carolina, for example, Penn gave the staff a PowerPoint presentation on a new approach in which Clinton would emphasize her commitment to solving specific problems.
Unimpressed, some staff members asked whether Clinton had already approved the plan; Penn said she had. Mandy Grunwald, who handles advertising, asked with frustration: "Why are we meeting about it then," according to one person who was present.
For months, senior Clinton aides went to Clinton and demanded that Penn's role in the campaign be diminished. They did not believe it was smart for him to serve as both pollster and strategist.
Clinton resisted, siding with Penn and letting him keep his broad portfolio. Even after Obama surged ahead of Clinton in February, Clinton replaced chief of staff Patti Solis Doyle rather than Penn.
It is unclear whether Penn's demotion will satisfy his detractors or stabilize the campaign in the crucial final months of the primary season.
"When you add to it the already contentious relationship he had with so many internally in the campaign and externally, he really should have been fired," one Clinton aide said Sunday, speaking on the condition of anonymity while discussing internal campaign dynamics.
Though he will no longer have the grand title of chief strategist, he will continue to "wield power," the aide said.
Other people close to the campaign suggested that out of loyalty or trust, Clinton had allowed Penn to harm her chances for the nomination.
"This is the fight of her life, and he didn't do her any great service by putting her in this position that she had to make this choice," said one person familiar with the campaign's operations. "You're on the one-yard line and you're pulling your quarterback."
Most uncertain is the effect that the heightened scrutiny of Penn's demotion may have on Clinton's attempts to woo working-class voters.
Union leaders have been complaining for months about the work Penn's firm has done for companies such as uniform manufacturer and launderer Cintas Corp., which Burson-Marsteller has helped to fight a unionization drive.
