To assess the significance of certain factors on a pressure groups success, it is first necessary to define what is meant by success. In the case of pressure or interest groups success can be defined by the effects caused on legislation, whether that be altering, blocking or helping pass it. Membership size is undoubtedly a key factor in a pressure groups success as a large size gives greater weight to a groups demands and allows a greater base from which resources and candidates can be drawn. There are other factors of significance such as the wealth of a group, the nature of government in power and the contemporary public opinion, which all contribute to the success of a pressure group, but ultimately the size of a pressure groups membership is the crucial factor in determining success since it indicates the support and the resources of a group and if large enough can span all political philosophies as to remain successful in times of partisanship. One argument that supports the notion of size being the crucial factor to a pressure groups success is that of if a pressure group has a large support base their demands carry more weight behind them, for example the AARP (American Association for Retired Persons) has over 37 million members therefore their demands will be much more adhered to by the government compared to a smaller group for fear of losing their support come election time. Practical examples of this include the statistics corroborated by the AARP indicating that senators in areas such as Arkansas and New York face the loss of up to 71% of the elderly electorate in their states if they vote in favour of social security changes. Furthermore, groups like the NRA which specifically has a large and dedicated membership, have been successful in derailing legislation due to the size of their membership, since they have been able to draw upon said membership