We illuminate the dynamics of primary campaigns by looking at how individuals changed their candidate support, favorability and viability within a crucial state in the 2020 primary. Via a multi-wave survey of likely primary voters in Michigan, we show that Joe Biden’s comeback win was due primarily to the change in perception of his viability following South Carolina and Super Tuesday, especially among the more moderate portion of the Democratic electorate. In subsequent county-level analyses we find that the difference between Bernie Sanders’s win in 2016 and loss in 2020 was more a function of changes in the Democratic primary electorate than in his appeal. Our work suggests that gains in viability do not benefit all candidates equally. Moreover, viability can be generated later in the schedule than previously thought and to decisive ends. We consider the implications of our findings for understanding Michigan’s outcome in November.

我们通过研究个人如何在2020年初选的关键状态下改变候选人的支持，好感和生存力来阐明初选运动的动态。通过对密歇根州主要选民的多波调查，我们显示乔·拜登的复出胜利主要是由于南卡罗来纳州和超级星期二之后，尤其是民主党选民中较为温和的部分，他对自己的生存能力的看法发生了变化。在随后的县级分析中，我们发现伯尼·桑德斯（Bernie Sanders）在2016年的获胜与2020年的失利之间的差异更多是因为民主党主要选民变化而不是他的呼吁所致。我们的工作表明，提高生存能力并不能平等地使所有候选人受益。此外，可以在进度表中比以前认为的要晚并且可以决定性地产生生存力。