The foreign policy crises that the USA has confronted under the administration of President Barack Obama have generated profound uncertainty about whether the USA can maintain what has been its consistent grand strategy since the end of the Cold War: primacy. The authors argue, drawing on a neoclassical realist framework, that this uncertainty has been driven not so much by fundamental changes in the international system itself, but rather by how such changes have been interpreted by the Obama administration and its critics. US grand strategy is now caught between approaches best described as the ‘decline management’ of the Obama administration and the ‘decline denial’ of president Donald Trump, which reflects the fracturing of the domestic ‘political support system’ that has underpinned primacy since the end of the Cold War.