Francis Thomas began his career by practicing law in Maryland following his admission to the bar and education at St. John's College. He gained legislative experience in the Maryland House of Delegates and later served in the United States House of Representatives, where he chaired the Committee on the Judiciary. Thomas held the governorship of Maryland, during which he unsuccessfully attempted to address the state deficit through unpopular tax measures. He returned to Congress and participated in the Maryland State Constitutional convention, representing various political affiliations over the years. Thomas also served as the Collector of Internal Revenue for Maryland and as the United States Minister to Peru, showcasing his diverse professional experience.

Francis Thomas's political career reveals a complex ideological positioning, blending staunch opposition to slavery with fiscal conservatism that led to unpopular tax proposals. His tenure as governor highlighted a tension between progressive social views and fiscally conservative measures. Thomas's rhetorical style, marked by a principled stand against slavery, contrasts with his legislative challenges in implementing effective economic policies. His involvement in infrastructure and foreign relations further illustrates an ideologically agile approach, navigating between regional interests and broader national concerns.