Out on the presidential campaign trail this year, candidates and commentators have had plenty to say about religion. Unfortunately, the conversation leaves a lot to be desired.

Sometimes the focus is misguided. In June, for example, the top three Democratic candidates participated in a televised forum on faith and national politics. The discussion focused on their personal piety - how often they pray, what they pray for and how faith has helped them through difficult times. John Edwards was even asked to name his biggest sin.

Other times, the topic is given short shrift. During the recent YouTube Republican debate, candidates had all of 60 seconds to explain whether they believe every word of the Bible.

Faith cries out for a more robust and fruitful conversation. Religion continues to play an important role in American life and politics, and it deserves serious and discerning discussion. Some questions about a candidate's faith are more appropriate and relevant than others to presidential responsibilities.

The more the candidates, the media and all Americans understand and exercise such discernment, the more likely we will be to achieve the Founders' vision for faith that informs and invigorates public life.

The most important consideration in discussing a candidate's faith is how it affects the ability to exercise a president's constitutional duties. How do the candidate's beliefs reconcile with acting as commander in chief of the U.S. military? How would they influence appointments of Supreme Court justices and foreign ambassadors? How about administering federal programs at odds with their personal beliefs, such as family planning?

In the 2000 election, for instance, vice presidential candidate Joe Lieberman was asked whether his Jewish faith would influence his foreign policy stance toward Israel. Similar concerns were raised about Pat Robertson's presidential bid in 1988, including questions about whether his Cabinet would be only filled with conservative Christians.

A second area of appropriate focus concerns the relationship between religious and political authority and identity. Americans would benefit from learning how a candidate's identity as a Baptist, a Roman Catholic, a Mormon or a Jew relates to his or her identity as an American. It also is significant how candidates see their religious authorities relating to the authority of the Constitution, which a president must pledge to uphold and defend. What would a candidate do if the two authorities were to conflict?

This issue was at center stage concerning the role of papal authority in John F. Kennedy's Roman Catholic faith. Similar concerns were raised about whether George W. Bush would be unduly influenced by evangelical leaders like Billy Graham - and they're now being asked of Mitt Romney concerning his church authorities.

Third, a healthier discourse would emphasize the ways in which faith shapes the candidates' thinking about fundamental political questions and informs their policy views. It's appropriate to ask candidates how their religious convictions shape their understanding of how the federal government should relate to institutions like families, churches and schools. It's also relevant to understand how they bring their faith to bear on issues such as immigration, marriage and health care. Candidates should be able to explain how they view the root causes of social problems or prioritize issues on the national agenda differently because of their faith.

Fourth, religious faith can be important as a source and shaper of a candidate's character. Hearing candidates talk about their faith might therefore help solidify perceptions of their moral integrity and ability to endure the inevitable strain of the presidency.

Knowing the personal attitudes and religious practices of candidates also can help voters to identify with them. But while questions about a candidate's prayer life and church attendance might enable some voters to see a significant aspect of their own lives reflected in their potential representatives, the value of such questions is limited for discerning national leadership potential. Politicians can testify to their own piety, but that's no guarantee they will act with integrity, speak honestly and avoid scandal once elected.

Religion's role in sustaining freedom, moral discernment and a healthy social order underscores the need for a serious conversation about faith in national politics. The current sound-bite debates, however, don't allow the kind of treatment these complex questions deserve. A more robust conversation would focus less on the self-professed piety of candidates and more on how their faith would influence their ability to serve as president. That's the kind of conversation in which the Founders could - and did - engage.

Ryan Messmore is the William E. Simon fellow in Religion and a Free Society at The Heritage Foundation (heritage.org).