Negatively framed political attitudes ("I don't like Romney") are stronger than positively framed attitudes ("I like Romney"), and this effect is strengthened when people think more deeply about the issues involved.

 

"Our prior research showed that framing an opinion in terms of opposition yields stronger attitudes than does framing it in terms of support. The most interesting point from our latest research is that this effect is actually stronger when people process the messages more deeply -- when they are motivated and have been able to think about the issue. But when people are not motivated and able, the effect goes away. So, perhaps counter-intuitively, the people who care the most about the issues or candidates seem more likely to be affected by the bias."