Looks like there is very little out there about their views of the UN. I did find this on Romney and Newt, but so far nothing from Santorum.
United Nations
Romney has been critical of the United Nations. In an April 2007 speech, Romney said, “the failures of the UN are simply astonishing.” He cited the United Nations Human Rights Council as an example of these failures. Still, Romney said, neither isolationism nor U.S. unilateralism are sound postures for foreign policy. “America's strength is amplified when it is combined with the strength of other nations.” ( SO! what does that mean?))
United Nations
Gingrich supports the ideals of the United Nations charter but believes that the organization itself is deeply corrupt and in need of reform. Gingrich served as co-chair with former senator George Mitchell on the United States Institute of Peace's Task Force on the United Nations, which issued a report calling for the abolition of the current UN Human Rights Commission and replacement with a new Human Rights Council[164] Gingrich sees the main problem at the United Nations being that a large group of developing countries, often referred to as the Group of 77, exploit the "one-country, one-vote" system in attempts to transfer wealth from the world's rich nations to themselves. Gingrich also points to fraud and embezzlement within the UN such as the Oil-for-Food scandal, anti-Western and anti-Israel bias within its human-rights organs, sexual assaults committed by peacekeepers, and a lack of sincere commitment to human rights as major problems that call for reform. Gingrich believes that the United States should spearhead an effort to reform the United Nations. Specifically, he calls for creating an independent oversight body, similar to corporate audit committees, to oversee financial matters, developing a clear-cut definition of terrorism emphasizing that violence against civilians is not acceptable, enhanced sanctions against human-rights violators, and a human rights body with rigorous standards for membership.[165]
Over the years, I've heard politicians talking about the failings of the UN, but "NO" condemnation of it. The people of this country"I think" especially the Republicans I know have nothing but disdain for the UN.I even know some party voting Democrats that think we should not be a part of it.