You guys don't get it...one of the most fundamental beliefs of the LDS Church is an individual's agency. Church members are taught doctrine until blue in the face, but ultimately it is an individual's righ to choose what to do and on Judgment Day there will be accountability for those choices.
Secondly, the LDS Church is very big on supporting the law of the land. For example, the Church is against war except when needed to defend home and family, but it never told members to dodge the draft in Viet Nam. Young men were told to obey the law and serve honorably.
Romney's position on abortion is no different. He is personally opposed to abortion, but, once again, it is the law of the land and individuals have the freedom to choose what to do. Furthermore, as governor he is hardly in any position to overturn Roe v. Wade.
Heck, if the people of MA, one of the most liberal states in the country, elected him as governor they must have liked him regardless of his religion.