WASHINGTON — When George Romney ran for the 1968 Republican presidential nomination, his Mormon heritage was mostly a footnote. It was scarcely mentioned in news accounts of the day. But for son Mitt Romney, the family religion presents a formidable political hurdle.

The younger Romney repeatedly is called on to defend his membership in The Church of Jesus Christ of Latter-day Saints and its teachings, encountering skepticism particularly from Christian conservatives, a key component of the GOP base.

"I believe that there are some pundits out there that are hoping I'll distance myself from my church so that'll help me politically. And that's not going to happen," Romney asserts.

Religion has not played so prominent a role in a U.S. national election since 1960, when John F. Kennedy became the first Catholic to be elected president.

And it's not only Romney under scrutiny. All the Democratic and Republican presidential hopefuls have been grilled on their religious beliefs. Most seem eager to talk publicly about their faith as they actively court religious voters.

Democratic Sen. Hillary Rodham Clinton emphasizes her Methodist upbringing and says her faith helped her repair her marriage.

Chief rival Sen. Barack Obama frequently uses the language of religion and proclaims a "personal relationship" with Jesus Christ. The Illinois Democrat — whose middle name is "Hussein" — scoffs at suggestions of Muslim leanings because he spent part of his childhood in Indonesia. He is a member of the United Church of Christ.

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In the most recent Democratic debate, a pastor in a YouTube video asked Democrat John Edwards to defend his use of religion to deny gay marriage. The former North Carolina senator — a Methodist — talked about his faith and his "enormous conflict" over the issue