Ambiguity – the capacity to have multiple meanings – is endemic to politics. Ambiguity creates political opportunities, structures debates and provides leeway for political entrepreneurs to advance their interests. I use the 2012 passage and 2014 rollback of reforms to the National Flood Insurance Program to show how ambiguity enables political entrepreneurship. In this puzzling case, Congress enacted and rolled back changes that threatened to impose politically unpalatable costs. Using semi-structured interviews and congressional testimony, I show how political entrepreneurs engaged with ambiguity in the buildup to the reforms’ passage. They used information strategically to interpret problems, solutions, rules, and goals; shape legislators’ perceptions of the reforms’ political implications; and adapt their arguments to the policy windows that opened. The case shows that ambiguity facilitates policy reform, but the direction of change depends on the priorities that are salient when a policy window opens and on the interests of political entrepreneurs.