In his now-classic research on inoculation theory, McGuire (1964) demonstrated that exposing people to an initial weak counterattitudinal message could lead to enhanced resistance to a subsequent stronger counterattitudinal message. More recently, research on the valence-framing effect (Bizer & Petty, 2005) demonstrated an alternative way to make attitudes more resistant. Simply framing a person's attitude negatively (i.e., in terms of a rejected position such as anti-Democrat) led to more resistance to an attack on that attitude than did framing the same attitude positively (i.e., in terms of a preferred position such as pro-Republican). Using an election context, the current research tested whether valence framing influences attitude resistance specifically or attitude strength more generally, providing insight into the effect's mechanism and generalizability. In two experiments, attitude valence was manipulated by framing a position either negatively or positively. Experiment 1 showed that negatively framed attitudes were held with more certainty than were positively framed attitudes. In Experiment 2, conducted among a representative sample of residents of two U.S. states during political campaigns, negatively framed attitudes demonstrated higher levels of attitude certainty and attitude-consistent behavioral intentions than did attitudes that were framed positively. Furthermore, the effect of valence framing on behavioral intentions was mediated by attitude certainty. Valence framing thus appears to be a relatively low-effort way to impact multiple features associated with strong attitudes.