Add to the mix persistent—although often-refuted—rumors linking the incumbent to Islam, and this year's presidential election holds the potential to break new ground in terms of discussions about politics and religion.
Denison, theologian-in-residence with the Baptist General Convention of Texas, recently wrote a paper, "The Faith of the Candidates," that specifically addresses questions about Obama's alleged ties to Islam and Romney's Mormonism.
"Obama has made history in a variety of ways, among them the fact that he was the first president not to be raised in a Christian home," Denison writes. "His biological father rejected the Islam of his birth, while his stepfather was Muslim more in name than in practice. His maternal grandparents, in whose home he spent many of his formative years, were Unitarians; his mother was an agnostic."
As a community organizer in Chicago, Obama attended Trinity United Church of Christ, where he made a public profession of faith in Christ and was baptized. Since his election, Obama and his family have not joined a church in Washington, D.C., but have worshipped primarily at Evergreen Chapel at Camp David.
In books, public speeches and interviews, Obama repeatedly has declared himself a Christian who believes "in the redemptive death and resurrection of Jesus Christ."
Even so, critics have continued to label Obama a closet Muslim who has kept his faith secret but has worked to advance Islamic causes. Denison notes the leap of logic required to accept that premise.
"If Obama had become a Muslim and now professes to be a Christian, he would be an 'apostate' to the Islamic world. To Muslims, there are three kinds of people—fellow Muslims, infidels (non-Muslims) and murtadd, apostates who left Islam for another religion," he writes. "The last group is to be shunned; some would seek their execution as traitors to the faith."
Denison notes Obama holds some theological positions contrary to evangelical beliefs. However, he writes, "When people repeatedly and consistently testify that they have asked Jesus Christ to forgive their sins and become their Savior and Lord, believers should take them at their word."
Likewise, he notes deep disagreement with Obama's positions on gay marriage, abortion rights and embryonic stem-cell research. "But President Obama is not the only Christian with whom I disagree on these issues," he writes.
Romney's Mormon faith presents evangelical Christian voters with a different set of questions, Denison notes: What do Mormons believe? Are they a cult? How would Mormonism influence Romney's presidency?
Mormon doctrine presents different views of God and Jesus than orthodox Christianity, relies on nonbiblical sources of authority and holds theological positions contrary to historically agreed-upon Christian doctrine.
"There is no question that Mormonism teaches a number of doctrines that are inconsistent with orthodox Christian theology," Denison writes.
He acknowledges some Mormons do not understand fully what their church teaches and may have asked Jesus to forgive their sins and become their Lord and Savior. He also points out Romney's service for two and a half years as a Mormon missionary in France and his longtime church involvement at multiple levels of leadership.
"In short, Mitt Romney has been fully engaged in Mormon practices his entire life. What the Mormon church officially teaches, we can assume he believes," Denison writes.
However, he notes, Mormon doctrine affirms "free agency"—the responsibility and right of each Mormon to determine his or her own beliefs—and Romney has a track record of independent thinking, having taken some political positions at odds with official church teaching.
"Judging from Romney's conflicts with Mormon leaders and his repeated affirmation of a free church in a free state, it seems that his Mormonism would not wield an undue influence on his policies or leadership in the White House," Denison writes.
Religious convictions influence a person's worldview, which provides the foundation for character and decision-making, he notes. At the same time, no candidate should be elected solely because of his faith or opposed solely on that basis.
"While I disagree with Mitt Romney's church on numerous points, I cannot identify any Mormon doctrines that affect directly the office of president," Denison writes.
"Romney's positions on key faith issues are likely to find support with conservative Christians. Many in more moderate or liberal traditions will reject some of his positions. But these positions are not uniquely the product of his Mormon beliefs."
Christians have a responsibility to make informed decisions as citizens, but their responsibility does not end once their ballots are cast, Denison insists.
"It is our duty not only to vote for the candidate whom we believe would best lead our nation, but also to pray for whoever wins this election," he writes. Christians should be "salt and light," regardless whether they agree with elected leaders.
Furthermore, Christians "are forbidden by God's word from slandering others, including our elected officials," he adds.
"Presidents retire from office, but the King of Kings reigns forever," he concludes.