We show that the polarized pumping can be used to control the relative powers of two linear, orthogonally polarized, eigenstates in a Yb:YAG laser. The experimental observations are in full agreement with a two-mode rate-equation model, highlighting the roles of both the gain anisotropy and the cross-saturation parameters, whose values are found to be ε=0.08 and β = 0.64, respectively, in a longitudinally pumped continuous-wave microchip laser. The application to dual-polarization frequency combs is discussed.