I see no reason to attribute conservative opposition to New START to anything other than conservative opposition to all treaties. ~Jonathan Bernstein 
As Patrick Appel says , Senate Republicans have not always been so reluctant to support arms control treaties. Kyl is a good example of this . The Moscow Treaty negotiated and signed by George W. Bush was ratified without a single Senator voting against it, and it reduced both arsenals much more than New START will, and it had no verification provisions. Kyl praised  the simplicity and genius of SORT at the time. We are now treated to endless complaints from Kyl and others that New START’s verification provisions are inadequate.
A distinction needs to be made between Senate Republicans, who have typically supported Republican Presidents’ arms control treaties in the past and have now gone into opposition, and conservative activists and hard-line former officials who are opposed to arms control as such (e.g., John Bolton, Richard Perle, etc.). There was opposition to the treaties negotiated by Reagan and Bush from conservative activists and lower-level officials, but the difference this time is that those lower-level former officials are now treated as authorities by Senate Republicans when they were previously overruled or dismissed. It seems to me that this is the real political significance of Republican opposition to the treaty that goes beyond anti-Obama positioning. The older generation of Republican realists and internationalists is passing away, the hard-line deputies who filled the lower ranks of previous administrations have depressingly become the new Republican authorities on national security, and they are providing movement conservatives with ready-made talking points that flatter the movement’s conception of itself as one that takes national security very seriously.
It is telling for the future of the GOP that all of the likely 2012 presidential candidates, except for Gary Johnson, flatly oppose the treaty. Somehow opposing New START has become a requirement for rising Republican leaders to establish their credibility on national security in the eyes of movement conservatives. Instead of rejecting the Bush administration’s foreign policy for its recklessness, aggression, and waste of resources, most Republicans seem to have convinced themselves that the main problems with the Bush years were lack of zeal and too much willingness to accommodate other states in the second term.
Update: I should add that Michael Krepon  made a very similar argument about the intra-GOP situation last month, and part of that post was in the back of my mind when I was writing this.