Four Republican presidential candidates appeared before a gathering of pro-life activists in New Orleans Friday.

Sen. Marco Rubio, R-Fla., and former Sen. Rick Santorum, R-Pa., joined former Texas Gov. Rick Perry and Dr. Ben Carson at the 2015 National Right to Life Convention to articulate their opposition to abortion.

"We often hear at conferences like this that an unborn child can't vote and can't speak," Rubio told conference-goers. "It's an important point, but I'd like to argue that it's actually not true. They can speak. They speak through you."

According to Rubio, who has repeatedly sponsored anti-abortion legislation in the U.S. Senate, the issue of abortion is "more than political or policy-related."

"It is a definitional issue about the kind of country we want to be," he said, adding that "America must stand for the belief that all life is worthy of protection, because all life comes from God."

The senator unabashedly declared himself "proudly pro-life" during his presidential announcement in April and has a voting record to back it that claim. While serving in the Florida state legislature, Rubio backed legislation requiring that doctors first perform ultrasounds on women seeking abortions and he recently voiced his support of a bill in the Senate that would create a federal ban on abortion after 20 weeks of pregnancy.

In Friday's speech, Rubio said being pro-life means going beyond abortion to defend the dignity of a child's life and bringing to them "the hope of the American Dream."

"We must defend the values that will give that child a shot at succeeding in society, and at one day starting a successful and rewarding family of their own," he said.

The top-tier candidate has outlined a conservative economic and national security agenda in several policy speeches already. But his appearance at the NRLC Convention was the first time the Florida senator shifted the focus to his socially conservative abortion views since launching his presidential bid.