Since the 2000 Census, the Census Bureau has contracted a paid advertising campaign to reduce the costs of Nonresponse Followup (NRFU) by increasing awareness of, and self-response to, the decennial census. Research that has examined the impact of paid advertising on self-response rates, however, has produced mixed results. This is in part because the environment of information surrounding the decennial enumeration period is complex and dynamic. In this paper, I used time-series data from the 2020 Census Tracking Survey to examine the effect of two key events on census awareness and intention to participate in the 2020 Census: 1) the launching of the national advertising campaign and 2) the initial round of 2020 Census mailings. Using an interrupted time-series approach, I found evidence that advertising increased awareness somewhat (less than 2%), but that the mailings produced a 10% shift. There was no evidence that advertising boosted intention to participate, although the mailings led to a nearly 10% increase. These results, taken together with the already existing body of mixed results, suggest a need to research the marginal costs and benefits of further expanding the Census Bureau’s paid advertising efforts relative to the costs and benefits of more intensive NRFU activities for targeted groups.