This study examines the public's motivated reasoning of competitive messages about sugary drink taxes, a public health policy approach attempted with some recent success in the United States. In an experiment embedded in a nationally representative survey fielded in the fall of 2012, we randomized participants (N = 5,147) to receive one of four messages: control, a strong protax message, a two-sided message, or a message refuting arguments made in soda company antitax messages. The protax message showed no effects on tax support, while the two-sided message depressed Republicans' support. The refutation message boosted independents' support but produced backlash among Republicans. This motivated response was pronounced among Republicans who were plausibly previously exposed to the sugary drink tax debate. These findings reinforce the communication challenges in an increasingly politicized US health policy discourse.