As the battle for the Republican and Democratic nominations for president begins to heat up, most candidates, especially GOP ones, are discussing their faith. Four likely contenders for the Republican nomination are Catholic—Jeb Bush, Marco Rubio, Rick Santorum, and Bobby Jindal. Jindal, the governor of Louisiana, recently argued in a New York Times op-ed that his “faith-driven” perspective led him to oppose gay marriage and to support legislation to “prohibit the state from denying a person, company, or nonprofit group a license, accreditation, employment, or contract . . . based on the person or entity’s religious views on the institution of marriage.” Several other GOP hopefuls are evangelicals—Ted Cruz, Scott Walker, Mike Huckabee, and Ben Carson. Hillary Clinton, the leading candidate for the Democratic nomination, has declared that the Methodist commitment to social justice directs her approach to politics.

Should prospective voters care about candidates’ religious convictions? Do the religious commitments of politicians significantly impact their worldviews, political philosophies, policies, and actions? Substantial evidence indicates that faith does matter. As Jindal’s example indicates, the faith of many of these candidates has affected their work as governors or senators. 

Moreover, the historical record strongly suggests that, if one of these candidates is elected president, his or her faith will continue to powerfully influence his or her work. Many chief executives, from George Washington to Barack Obama, have exhibited a deep and meaningful faith that has helped shape their character, thought, and actions. Presidents’ worldviews determines what they highly value and their perspectives on human nature, morality, and social causality.

Presidents’ religious commitments have often affected their policies and decisions. Examples abound. Washington’s faith led him to provide religious liberty for Catholics and Jews in the nascent nation. Inspired by their understanding of theology and history, Thomas Jefferson and James Madison worked to separate church and state. His perspective of the cultural mandate prompted the deeply devout John Quincy Adams to propose funding roads, canals, and educational institutions to expand and enrich the United States. William McKinley, a pious Methodist, explained that his decisions to declare war against Spain in 1898 to end the oppression of Cubans and to urge the Senate to take control of the Philippines the next year were bathed in prayer and inspired by Christian humanitarianism. Woodrow Wilson’s staunch Presbyterian convictions guided his work in devising the Treaty of Versailles. Quaker convictions helped motivate Herbert Hoover to reform prisons and protect civil liberties.  

Consider more examples: Franklin Roosevelt, who served as the senior warden of the St. James Episcopal Church in Hyde Park, New York, during his entire presidency, repeatedly urged Americans to promote social justice and called for spiritual renewal. Their religious convictions led Harry Truman, Dwight Eisenhower, John F. Kennedy, and Ronald Reagan to view the Cold War as a battle to preserve Christianity against the onslaught of atheistic communism. Bill Clinton’s efforts to increase the opportunity for religious expression in public schools and the workplace, support for welfare reform, and quest to mediate disputes in the Middle East were stimulated in large part by his Southern Baptist beliefs. Obama’s stances on healthcare, gay marriage, and poverty are based on his progressive Protestant convictions. Again and again, he has urged Americans to be their “brothers’ keeper.” Numerous presidents, including Madison, Wilson, McKinley, George H. W. Bush, and George W. Bush, used just war arguments to defend American participation in military actions.

The expectations of prospective voters (polls consistently report that most Americans prefer presidents who have a strong faith in God) prompts presidential candidates (and other politicians) to frequently employ religious language to appear virtuous and honest, enhance their popularity, win elections, and gain support for their policies. Consequently, disentangling what presidential candidates and chief executives actually believe from what they say simply to please the public and gain political advantages is difficult. However, by closely studying their lives before, during, and after their time in office, scrutinizing their private as well as public statements, and considering the testimony of others who knew them well, we can get a better idea of their true convictions. Their religious beliefs are important because, as argued, they shape their character, understanding of the world and people, and policies.

Therefore, prospective voters should evaluate the faith of candidates and how it has affected their work as governors or senators. Their faith is likely to significantly influence how they will function in the Oval Office. 

Our weekly feature Then and Now harnesses the expertise of American religious historians who care about the cities of God and the cities of humans. It's published in partnership with the Kripke Center of Creighton University and edited by Edward J. Blum and John D. Wilsey.

This article was edited for additional clarity on May 20, 2015.