In this excellent article by Glen Greenwald, posted on his blog, he points out that both Romney and Guiliani were asked by the Club for Growth if they thought that the President should have the power to imprison Americans without any review. Romney said he would have to consult a team of lawyers and Guiliani said that he would hope to use such power infrequently. As Greenwald points out that means that two of the three leading Republican candidates for their party's nomination seem to believe that it is not un-American for the President to imprison American citizens without any review by the courts.
The Republican Party is becoming the party of right-wing authoritarianism, although perhaps "becoming" is really not the right word. Perhaps the phrase should be "continuing to be". It is incomprehensible that a person who is running for an office that requires the holder to take an oath to protect the Constitution would believe in something that is clearly unconstitutional.
Such a belief is not at all "conservative". It is instead very radical. It is radical to suggest that the President has the power to detain American citizens without review by someone independent of the executive branch. Such review is one of the pillars of the rule of law in this country. Candidates who believe otherwise shouldn't be elected.