From Christopher Thompson :
But Harrington's argument was not "the product of an analysis of the contemporary distribution of land, because it does not claim to be" such: it was an investigation of the decline of feudal tenures and the development of freehold tenure, which made possible a state in which a Classical Republic of the kind described by Livy and advocated by Machiavelli. Scholars like J.G.A.Pocock and Judith Schklar showed as long ago as the 1950s that Tawney's view of Harrington was erroneous.
Reply thehistorywoman (http://thehistorywoman.wordpress.com/)
I'm not saying that Harrington's thesis is based on an exact or even correct 'analysis of the contemporary distribution of land'. But he did perceive significant changes which - as you rightly say - were caused by 'the decline of feudal tenures'. And this decline of feudal tenures gave rise to a new type of landownership and at the same time a new type of society characterised increasingly by merit rather than birth. The senators who replace the old lords in Harrington's ideal state hold their office because they are 'wiser than the rest', not by the virtue of their birth. That is what matters. Changes in property ownership produce changes in a country's power structures. In the long term freehold tenure facilitates popular participation in politics.