denying that the New Deal was "attempting to commit the nation to any ism or ideology except democracy, humanity and the civil liberties which form their foundations."America's presidents are right to wish to ward off ideology, but they protest too much about its absence, for ideological battles have been plainly important in recent presidential politics. Obama may not be an ideologue, but his attempt to transcend ideology, proclaimed in his Inaugural Address, was merely an inducement to a starkly ideological, and highly successful, reaction to the leadership initiatives of his first two years. As a result of the "asymmetric polarization" between the major parties, the Republicans, led by a new generation of assertive House members, has moved closer than ever before toward ideological purity (Kabaservice 2012, 3385-88; Mann and Ornstein 2012, xi, 8-15, 51-58). In his predecessor's presidency, ideological battle was waged within the administration, where the "unrestrained ideological entrepreneurship" (Campbell 2004, 13) of a clique of neoconservatives (neocons) helped propel the nation to a discretionary war in Iraq (Halper and Clarke 2004). Finally, going back to the 1980s, ideological credentials were prized by the Reagan administration in making administrative and judicial appointments (Aberbach et al. 1990;Langston 1992;O'Brien 1988;Weatherford and McDonnell 1990), and the president's own beliefs and behavior inspired debate over the extent to which Ronald Reagan was himself an ideologue (Hantz 1996;Langston 1992;Shimko 1992).Despite considerable scholarship on ideology and modern American politics, little is known about how such moments of ideological intensity and conflict might relate to one another, about what happens, that is, at the intersection of ideology, ideologues, and the modern presidency. This article seeks to explore this point of intersection. I proceed first with definitions and conceptual clarifications, identifying strengths and weaknesses in conventional usages of the terms "ideology" and "ideologue." A functional analysis comes next, to uncover the numerous ways in which ideology and ideologues might be expected to influence the modern presidency. Ideology, understood as a distortion of ideas and a distinct cognitive style, turns out to have a place in the presidency at the juncture of crisis, the institutional environment of the presidency, presidential personality, and regime characteristics. Because each of these factors is complex and, to a large degree, independent, ideological influence in the presidency is episodic, following no simple pattern, as will become apparent in a selective narrative of ideological influence in the presidency from Roosevelt to Obama. Ideology's quintessential elusiveness, I argue in conclusion, reflects and sheds light on the contingent dynamics of the presidency.