ANN ARBOR, Mich.—Political leaders regularly promise to "fight" for noble causes and "combat" pressing problems. They declare "war" on social problems, such as poverty, disease, drugs and terrorism. This violent political rhetoric—whether politicians intend to or not—can enflame violent attitudes in many Americans, especially those predisposed to behave aggressively in daily life, according to new University of Michigan research involving three studies. "The results presented here clearly refute the claim that violent political rhetoric is without negative consequences," said Nathan Kalmoe, a U-M political science doctoral candidate and study's author."The evidence might be sufficient to make political leaders think twice before infusing violent language into speeches and ads, particularly in situations when their audiences are already boiling over with hostility." The debate about violent language intensified earlier this month when a 22-year-old man allegedly shot and killed six people, while injuring more than a dozen others in Arizona, including U.S. Rep. Gabrielle Giffords.Kalmoe conducted two national surveys and a local study before the 2010 mid-term elections to analyze attitudes about political violence.While most people strongly rejected political violence, at least 15 percent of the respondents agreed with one or more violent statements. Party affiliation played no role; Democrats and Republicans were equally likely to express support for political violence. Individuals predisposed to behave aggressively in social interactions reported violence levels several times greater than peers with low aggression scores.In Kalmoe's first national survey, 412 adults read two television advertisement texts (one violent, the other non-violent) for two U.S. House candidates. The candidates were not identified by name or party. Words involving violence were changed within the text. In contrast to the most extreme examples of violent language in politics, the words in the experiments were mild. They included fighting/struggling, fight/work, and battle/race. In addition, no person or group was targeted in the ads. Respondents were asked about their aggression levels and interest in violence against political leaders. Those who were aggressive had strong predispositions to support political violence, and that increased when exposed to violent rhetoric, the research indicated. Young adults were more likely to adopt violent attitudes after exposure than older adults. The second study was done in late summer 2010 with 512 adults who were exposed to one advertising text instead of two. Nearly 13 percent of respondents endorsed political violence, regardless of party affiliation. The results in the second study also found that violent rhetoric greatly increased support for political violence among aggressive young adults, but had no significant effects among other subjects.A sample of 384 college students responded to the third study in late summer/fall 2010. Unlike the other studies, respondents were told that the text came from a Republican or Democrat running for the U.S. House. They were also randomly given violent or non-violent text.Students supported political violence at levels similar to those questioned in the national samples. Aggression was a weak predictor of violent attitudes, and partisanship remained unrelated in the findings, Kalmoe said. As in the two national studies, violent language increased support for political violence among aggressive students. Participants reacted similarly to the ads whether they were attributed to a Democrat or a Republican. Although the studies showed that violent political language had strong effects on violent attitudes, they did not test whether violent behavior was more likely. Even so, violent attitudes are a worrisome sign of incivility in politics, Kalmoe said.