The spread of online misinformation is increasingly perceived as a major problem for societal cohesion and democracy. Much attention has focused on the role of social media as a vector of misinformation. The role of political leaders has attracted less research attention, even though leaders demonstrably influence media coverage and public opinion, and even though politicians who "speak their mind" are perceived by segments of the public as authentic and honest even if their statements are unsupported by evidence or facts. Here we show that in the last decade, politicians' concept of truth has undergone a distinct shift, with authentic but evidence-free belief-speaking becoming more prominent and more differentiated from evidence-based truth seeking. We analyze communications by members of the U.S. Congress on Twitter between 2011 and 2022 and show that political speech has fractured into two distinct components related to belief-speaking and evidence-based truth-seeking, respectively, and that belief-speaking is related to spreading of untrustworthy information. We show that in tweets by conservative members of Congress, an increase in belief-speaking of 10% is associated with a decrease of 6.8 points of quality (using the NewsGuard scoring system) in the sources shared in a tweet. In addition, we find that an increase of belief-speaking language by 10% in the shared articles themselves is associated with a drop in NewsGuard score of 4.3 points for members of both parties. By contrast, increase in truth-seeking language is associated with a slight increase in quality of sources. The results support the hypothesis that the current flood of misinformation in political discourse is in part driven by a new understanding of truth and honesty that has replaced reliance on evidence with the invocation of subjective belief.

翻译：在线错误消息的传播日益被视为社会凝聚和民主的一个主要问题。人们越来越把注意力集中在社交媒体作为误导信息载体的作用上。政治领袖的作用吸引了较少的研究关注,尽管领导人明显影响媒体的报道和舆论,尽管公众部分认为“说出自己的想法”的政客是真实和诚实的,即使其言论没有证据或事实的支持。我们在这里表明,在过去十年里,政治家的真相概念发生了明显的变化,真实但没有证据的信仰依赖变得更加突出,与基于证据的真理寻求更加不同。我们分析了2011年至2022年美国国会成员在Twitter上的沟通,并表明政治言论已经分裂成两个不同的部分,分别与讲信仰和基于证据的真相寻求有关,而那些说信仰的言论是真实的。我们在保守党员的推特中显示,说信仰增加10%的信念与基于事实的信念的下降有关(使用NewGuard评分系统 ) 。在推特上我们分析了美国国会议员的沟通沟通信息质量。此外,在推特中我们发现,通过分享的言语中的言语增加了一个比值。