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tokens: The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Support for this work was provided by the NSF through the Grote Reber Fellowship Program administered by Associated Universities, Inc./National Radio Astronomy Observatory. This research was also supported by the NASA Ames Research Center via Cooperative Agreements NNA09DB30A, NNX15AD20A, and NNX16AF59G to J.O. Burns. The authors like to especially thank J. Aguirre for his constructive feedback on the formalism of our approach and discussions on other aspects related to the foreground polarization. The authors would also like to thank R. Monsalve for his comments on the instrumental aspects of the approach. The authors gratefully acknowledge J. Mirocha for providing the simulated global 21 cm data using ARES. B.D. Nhan is also grateful to K. Tauscher and R. Monsalve for their assistance in utilizing the sky map data.