  This paper is devoted to a deep analysis of the process known as Cheeger
deformation, applied to manifolds with isometric group actions. Here, we
provide new curvature estimates near singular orbits and present several
applications. As the main result, we answer a question raised by a seminal
result of Searle--Wilhelm about lifting positive Ricci curvature from the
quotient of an isometric action. To answer this question, we develop techniques
that can be used to provide a substantially streamlined version of a classical
result of Lawson and Yau, generalize a curvature condition of Chav\'ez,
Derdzinski, and Rigas, as well as, give an alternative proof of a result of
Grove and Ziller.
