Sen. John McCain on Sunday came out against affirmative action, and endorsed ballot measures to bar public colleges and universities -- and other state agencies -- from considering race in admissions or hiring.

McCain had previously been among those Republicans who refused to endorse these ballot measures.

His comments on Sunday came in an appearance on the ABC News show "This Week," which also revealed that a decade ago, he called efforts to bar affirmative action "divisive." On Sunday, asked if he would back the ban on affirmative action that will be considered by Arizona voters this fall, he said: "I support it. I do not believe in quotas.... I have not seen the details of some of these proposals. But I’ve always opposed quotas."

In a separate appearance, Sen. Barack Obama, McCain's Democratic opponent for the presidency, supported affirmative action, but also continued to state that it is not the primary solution for anyone. Obama has said several times during the campaign that he believes class in addition to race should be considered.

"I am a strong supporter of affirmative action when properly structured so there is not a quota, but it is acknowledging and taking into account some of the hardships and difficulties that communities of color may have experienced, continue to experience, and it also speaks to the value of diversity in all walks of American life," he said Sunday. "I've also said that affirmative action is not going to be the long-term solution to the problems of race in America, because, frankly, if you've got 50 percent of African American or Latino kids dropping out of high school, it doesn't really matter what you do in terms of affirmative action. Those kids aren't going to college."

McCain's opposition to affirmative action is winning him points in conservative circles, but drawing criticism from defenders of affirmative action in higher education. In particular, they object to his equating affirmative action with quotas.

"Changing one’s mind is certainly the American way but changing positions to garner support from a particular population should be questioned even by those who oppose affirmative action. Moreover, using affirmative action as a wedge issue only divides our nation when it is time to bring us together," said a statement from ReNee Dunman, director of equal opportunity and affirmative action at Old Dominion University and president of the American Association for Affirmative Action. (The association is non-partisan and does not endorse candidates for office.)

On the issue of quotas, Dunman added: "Once again, I am compelled to dispel the myth that affirmative action requires quotas -- they are unlawful and expressly prohibited by federal regulations." She noted that many affirmative action plans have goals, but that such goals do "not require hiring or admitting a particular number of women or minorities."

Affirmative action is the second diversity-related issue on which McCain has shifted during the campaign, although he may be switching sides again on the other issue: the federal DREAM Act to help students who cannot document their legal immigration status.

McCain was one of the key forces behind immigration reform legislation last year that for a time would have included the DREAM Act (Development, Relief and Education for Alien Minors), which would have provided a pathway to permanent residency for undocumented students who complete two years of college or military service. For students who came into the country illegally before age 16 and have lived in the country for five years, the DREAM Act would have for the first time given undocumented students access to federal loans and work study programs (but not federal grants).

When many Senate Republicans challenged the immigration reform measure, and many conservative activists denounced McCain for backing it, the larger piece of legislation was blocked, but many educators then backed a plan to push the DREAM Act by itself. But during meetings to try to repair his ties to conservatives, McCain pledged to oppose the DREAM Act solo, saying: "I got the message and the American people want the borders controlled first."

This month, however, in answering questions from a Latino group, McCain said he approves of the DREAM Act.

Obama has consistently supported the DREAM Act.