Context: Early childhood education (ECE) programs enhance the health and social wellbeing of children and families. This preregistered, randomized, controlled study tested the effectiveness of communication strategies to increase public support for state investments in affordable, accessible and high-quality child care for all. Methods: At time1 (August-September 2019), we randomly assigned members of an online research panel (n = 4,363) to read one of four messages promoting state investment in child care policies and programs, or to a no-exposure control group. Messages included an argument-based message (“simple pro-policy”), a message preparing audiences for encountering and building resistance to opposing messages (“inoculation”), a story illustrating the structural nature of the problem and solution (“narrative”), and both inoculation and narrative messages (“combined”). At time 2 (two weeks later) a subset of respondents (n = 1,436) read an oppositional anti-policy message and, in two conditions, another narrative or inoculation message. Ordinary least squares (OLS) regression compared groups in levels of support for state investment in child care policies and programs. Findings: As hypothesized, those who read the narrative message had higher support for state investment in child care policies than those who read the inoculation message or those in the no-exposure control group at time 1. Among respondents who were initially opposed to such investments, those who read the narrative had greater support than respondents who read the simple pro-policy message. Those who received the inoculation message at time 2 were more resistant to the anti-policy message than respondents who did not receive such a message, but effects from exposures to strategic messages at time 1 did not persist at follow-up. Conclusions: Results offer guidance for those seeking to increase public support for early childhood policies and programs and could inform broader efforts to promote high-value polices with potential to improve population health.