This should be a big boost to Mitt Romney, as the gold standard of conservative thought endorses him:

Romney is an intelligent, articulate, and accomplished former businessman and governor. At a time when voters yearn for competence and have soured on Washington because too often the Bush administration has not demonstrated it, Romney offers proven executive skill. He has demonstrated it in everything he has done in his professional life, and his tightly organized, disciplined campaign is no exception. He himself has shown impressive focus and energy.

...Unlike some other candidates in the race, Romney is a full-spectrum conservative: a supporter of free-market economics and limited government, moral causes such as the right to life and the preservation of marriage, and a foreign policy based on the national interest. While he has not talked much about the importance of resisting ethnic balkanization — none of the major candidates has — he supports enforcing the immigration laws and opposes amnesty. Those are important steps in the right direction.