In 1760 a youthful John Adams noted in his diary that he had begin to read The Spirit of Laws and planned to compile comprehensive marginal notes to insure his proper attention to the work. Roughly a decade and a half later, Thomas Jefferson, who was to suceed Adams to the Presidency, devoted no less than twenty-eight pages of his Commonplace Book to extracts from this same work, and in 1792, in an essay on "Spirit of Governments," James Madison compared Montesquieu's role in the science of government to that of Francis Bacon in natural philosophy. According to Madison, Montesquieu "had lifted the veil from the venerable errors which enslaved opinion and pointed the way to those luminous truths of which he had but a glimpse himself." --quote without permission from the Preface to 1977 University of California Press edition of the Spirit of Laws (DO NOT BUY! Horribly Abridged!)As I mentioned earlier, George Washington studied Montesquieu and Blackstone for the Second Constitutional Convention. In addition, I've read John Jay and Alexander Hamilton also regarded the work quite highly.
So, when people who know too little point to the conservative John Locke (a lot of whose work was involved in the admirable task of refuting the Divine Right of Kings(1st Treatise on Government) and then setting up monarchical governments (Carolinian Constitutions)) point to Montesquieu.
It is the best way to shove the facts up the ass of the so-called originalists who fob off de Tocqueville and Locke and rose-colored glasses history on us until their eyes bleed.