"In you, oh God, we trust ... that you will keep us ever committed to protect the life and well-being of all people but especially unborn children, the sick and the elderly, those on skid row and those on death row," the archbishop said in the prepared text of the prayer.
He also touched on themes of social justice, such as helping the poor, providing adequate health care and education, and not discriminating based on race, gender, immigration status or faith.
The references to an anti-abortion stance, however, could draw the most interest. In the prayer, Mahony said he hoped all candidates would embody values that "protect all human life."
His invocation was delivered to an audience that largely believes in a woman's right to an abortion. He stressed, however, that the prayer was nonpartisan.
"I come as a pastor, not a politician; an advocate of values, not candidates," he said. "Prayer must be about moral values, not partisan politics. It should express faith, not ideology."
That he delivered the prayer at all was a break from recent precedent.
In Chicago in 1996, the late Cardinal Joseph Bernardin turned down an invitation to speak at the Democratic convention. In New York, the late Cardinal John O'Connor did the same during Democratic Party gatherings there in 1984 and 1992.
Their decisions were widely perceived to be a reaction to Democratic support of abortion rights.
Mahony, who previously denounced the 1998 political campaigns as "anti-life," was invited to deliver the invocation last week by Vice President Al Gore.
Democratic Party leaders said the church's anti-abortion stance would not dampen enthusiasm for Mahony's participation.
"He's a religious man ... and that is their position," said Bob Mulholland, spokesman for the California Democratic Party and a fellow Catholic. "But the great thing about America is that religious leaders are focused on the afterlife, while elected officials are focused on the daily life of average Americans, and average Americans struggle with that issue."
The Democratic Party, he said, remains "overwhelmingly pro-choice."