The vast majority of scholarship on foreign aid looks at either the effectiveness of foreign aid or why particular countries receive aid from particular donors. This paper takes a different approach: what are the domestic sources of support for foreign aid? Specifically, how does the donor's domestic political and economic environment influence ‘aid effort’? This paper uses a time-series cross-sectional data set to analyze the influence of changes in political and economic variables. As governments become more conservative, their aid effort is likely to fall. Domestic political variables appear to influence aid effort, but only for aid to low income countries and multilaterals while aid effort to middle income countries is unaffected. This suggests that models solely emphasizing donor economic and international strategic interests as determinants of donor aid policy may be mis-specified. These results also suggest sources of aid volatility that might influence recipient growth prospects.