Rubio, the Florida senator, is not the only GOP presidential contender to shun the widely accepted exceptions, which also include when a pregnancy threatens the mother's life.
But for a candidate whose campaign has been designed to appeal broadly to general-election voters, it is a bold distinction that could hurt him with female voters.
Rubio's sharpened position emerged during the first Republican primary debate Thursday night in Cleveland as the candidates fielded questions about defunding Planned Parenthood, and he expanded on it Friday in an interview on CNN.
“I personally believe that you do not correct one tragedy with a second tragedy,” Rubio said. “I believe all human life, irrespective of the circumstance in which it came into being, is worthy of protection.... If I have to weigh the two equities here, I have to err on the side of life.”
Rubio has positioned himself as an antidote to the candidates of “yesterday” — how Rubio, 44, refers to Democrat Hillary Rodham Clinton, 67.
When pressed on whether his view puts him out of step with contemporary voters, Rubio fought back in a spirited exchange by saying that life begins at conception and, as a Catholic, he believes it must be protected in all circumstances.
“The value of life is timeless,” he said.
Strategists believe that Rubio emerged from the debate perceived as a competent and qualified candidate, with an optimistic message that contrasts with others on stage and could have appeal beyond Republican primary voters.
And though it's a risk for the general election, his position on abortion could help him peel away conservative and evangelical voters in the crowded 17-candidate primary field that includes other social conservatives.
Wisconsin Gov. Scott Walker is already on record as rejecting the abortion exceptions, as is Mike Huckabee, the former Arkansas governor who has a strong backing from evangelicals.
Rubio was careful to say that his views on abortion are “personally how I feel,” which provides potential space between his beliefs and governing strategy.
But voters do not always hear such distinctions.
During the debate, Rubio objected to Fox News moderator Megyn Kelly's question about how he squares his support for abortion exceptions with his Catholic faith.
“I'm not sure that's a correct assessment of my record,” Rubio said.
“You don't favor a rape and incest exception?” Kelly asked.
“I have never said that. And I have never advocated that,” Rubio said. “What I have advocated is that we pass a law in this country that says all life at every stage of development is worthy of protection.”
Rubio has backed legislation that included the exceptions as part of broader abortion prohibitions on later-term abortions.