Republican presidential candidate Herman Cain has signed the Susan B. Anthony List's anti-abortion pledge, leaving Mitt Romney as the only major candidate who hasn't done so.
The "Pro-Life Presidential Leadership" pledge commits candidates to abide by four pro-life goals if elected to the presidency.
That leaves Romney, whose past support for abortion rights makes him suspect to many conservatives, as the sole outlier.
Romney has consistently led the GOP presidential race, but remains suspect with many conservative voters. Different candidates from the right have challenged Romney for the lead, with Gingrich now seen as a top contender.
Cain, an associate Baptist Minister at Antioch Baptist Church North in Atlanta, explained his decision by saying he was "100 percent pro-life" and believes that "all human beings have intrinsic dignity."
"Where my powers in the Executive Branch are concerned, I will work at all times to oppose government funding of abortion," he told the SBA List. "I will veto any legislation that contains funds for abortions. I will do everything that a president can do constitutionally to advance the culture of life."
The pledge specifically commits candidates:
• FIRST, to nominate to the U.S. federal bench judges who are committed to restraint and applying the original meaning of the Constitution, not legislating from the bench;
• SECOND, to select only pro-life appointees for relevant Cabinet and Executive Branch positions, in particular the head of National Institutes of Health, the Department of Justice, and the Department of Health & Human Services;
• THIRD, to advance pro-life legislation to permanently end all taxpayer funding of abortion in all domestic and international spending programs, and defund Planned Parenthood and all other contractors and recipients of federal funds with affiliates that perform or fund abortions;
• FOURTH, advance and sign into law a Pain-Capable Unborn Child Protection Act to protect unborn children who are capable of feeling pain from abortion.