WASHINGTON, June 4 (AP) - Despite disagreeing with George W. Bush on abortion, Pennsylvania Gov. Tom Ridge said Sunday it would be "my responsibility to back him up" if asked to be Bush's running mate. "I think my job is to be supportive of Governor Bush," Ridge said on ``Fox News Sunday," when asked whether he would continue speaking out for abortion rights if he joined the ticket. "I think it's pretty well documented ... that we disagree on that issue. "But in terms of his support as our national leader of that point of view, it'd be my responsibility to back him up even though I think people would know we disagree with that," said Ridge, a Republican in his second term. Bush, the likely GOP nominee for president, favors abortion only in cases of rape, incest or to save the woman's life. Ridge, also a Republican, backs abortion rights but opposes a certain type of late-term abortion. Ridge, who Bush has said is under consideration for the No. 2 job, has urged the party to remove strict anti-abortion language from its platform. Bush has said he does not want to amend the language, but realizes Republicans will disagree on the issue. In 1980, Bush's father, George Bush, an abortion rights supporter, adopted Ronald Reagan's anti-abortion stance after joining Reagan on the Republican ticket. Asked whether he would follow suit, Ridge said: "My job is to support the public posture of the president of the United States." Others disagreed on the prospect of Ridge as the Republicans' pick for vice president. Former Republican and Reform Party presidential hopeful Pat Buchanan said such a step would mark "the beginning of the end" of the GOP. "I think if (Bush) did do that he would permanently split the Republican Party. He would make the Republican Party basically indifferent on the issue of life," Buchanan said on Fox. Sen. John McCain, R-Ariz., a former GOP presidential contender who shares Bush's views on abortion, noted that Bush said he would not subject potential running mates to any litmus test. "The criteria is who can best serve as president of the United States," he said on NBC's "Meet the Press." "I believe that there should not be any single reason for him to be disqualified."