WASHINGTON — Two of the Republicans’ most conservative presidential hopefuls promised anti-abortion activists yesterday that if elected, they would work to overturn the Supreme Court decision legalizing the procedure.

Senator Brownback of Kansas and Rep. Duncan Hunter of California addressed the annual March for Life marking the anniversary of the 1973 Roe v. Wade ruling.

“We recognize a tragedy of life in Roe v. Wade, but that tragedy will not always stand,” Mr. Brownback told thousands of cheering abortion foes at an afternoon rally.

Mr. Brownback, who formally launched his presidential bid on Saturday, spoke about adopting his daughter, Jenna, from a Chinese orphanage.

“I mention her because some woman in China, who I probably will never meet, fought for her life,” Mr. Brownback said. “Somebody fought for her life. You are fighting for somebody’s life.

Mr. Hunter, who has established a presidential exploratory committee, told the crowd he and his wife would begin to campaign in earnest this Thursday in South Carolina, one of the earliest primary states.

“If we have a judicial applicant, a judicial nominee who can look at a sonogram of an unborn child and not see the value of human life … if I should become president of the United States, he will not receive a judicial appointment,” Mr. Hunter said.

Both lawmakers are viewed as long shots to win the nomination over better-known candidates like Senator McCain of Arizona and Mayor Giuliani. But each is aiming to corner the party’s social conservative base, which considers abortion a key issue.

Mr. Brownback later hosted a reception on Capitol Hill for about 200 of the activists.