That conclusion follows a sweeping 2014 Pew study that found that “partisan antipathy is deeper and more extensive” than at any point in the last two decades.

That negativity appears to have fed a growing perception that the opposing party isn’t just misguided, but dangerous. In 2016, Pew reported that 45 percent of Republicans and 41 percent of Democrats felt that the other party’s policies posed a threat to the nation.

The fear of what harm the other party could cause appears to be a major motivator behind party affiliation. “It’s at least as much what I don’t like about the other side as what I like about my own party,” said Jocelyn Kiley, associate director of research at the Pew Research Center.

When asked why they identified as Republican, 68 percent of respondents told Pew that a major factor was the harm that Democratic policies posed, just surpassing the 64 percent who cited the good that could come of their own party’s policies. Among Democrats, 62 percent said fear of Republican policies was a major factor for their affiliation, while 68 percent cited the good of their own party’s policies.

Independents, who outnumber members of either party and yet often lean toward one or the other, are just as guided by fear. More than half who lean toward either party say a major reason for their preference is the damage the other party could cause. Only about a third reported being attracted by the good that could come from the policies of the party toward which they lean.

Opposing partisans are also likely to find each other harder to reason with. Last year, Pew found that 70 percent of Democrats and 52 percent of Republicans considered members of the opposing party to be more close-minded than other Americans. Significant shares also considered opposing partisans exceptionally immoral, lazy and dishonest, though Democrats held those views somewhat less. About a third of either party viewed the opposition as less intelligent than other Americans.

Past surveys show that such views have worsened with time. Americans in 1960 were more likely to allow that members of the other party were intelligent, and they were less likely to describe opposing partisans as selfish.