Robert E. Lewis was born in 1857 in Cass County, Missouri, and studied at Westminster College in Fulton, Missouri. He entered the bar in 1880 and practiced law in Clinton, Missouri, while also serving as the prosecuting attorney for Henry County from 1883 to 1887. Lewis transitioned to the judiciary in 1903, serving as a judge in Colorado before being nominated to the United States District Court for the District of Colorado in 1906. He later served on the United States Court of Appeals for the Eighth Circuit and was reassigned to the Tenth Circuit in 1929, where he remained until assuming senior status in 1940.

Robert E. Lewis combines traditional fiscal responsibility with progressive environmental policies, suggesting a nuanced approach to economic and ecological issues. His advocacy for moderate tax reforms and sustainable development practices indicates an ideologically agile stance, balancing conservative fiscal principles with forward-thinking green initiatives. Lewis's commitment to equal educational opportunities and public health improvements reveals a progressive streak, yet his support for an independent judiciary underscores a conservative respect for institutional integrity. This juxtaposition of progressive social policies with conservative judicial principles creates an intriguing conceptual tension in his political identity.