With a goal to investigate the dynamics of online persuasion, this research extends the Elaboration Likelihood Model to determine the relative effects of argument quality as a central route to influence attitude change versus design elements (specifically image appeal, navigation design, and connectedness) as peripheral route cues to attitude change. Results emanating from this research are based on a broad sample of 390 participants who viewed a website about the merits of the Keystone XL oil pipeline. The findings indicate that in addition to argument quality, the design of the website can influence attitude change. Further, there are differences in how those with high or low prior knowledge of a persuasion topic are influenced. Of interest, change in issue involvement is less important for the high knowledge group, but for the low prior knowledge group it mediates the peripheral route impacts on attitude change.