Political analysts are closely monitoring President Trump’s approval rating to gauge the likelihood he’ll be reelected, but his perceived popularity will also have an important impact in shaping the Democratic primaries.

I remember back in 2008, speaking to a Democratic voter ahead of the Iowa caucus, who explained to me that everybody knew that Democrats were going to win the presidential election that year, so they had the luxury of picking whichever candidate they liked best. At the time, Democratic voters had reason to be confident. The party had taken over both chambers of Congress in 2006, the Iraq War remained unpopular, and George W. Bush’s approval rating had spent months bouncing around the high 20s to low 30s. Republican candidates were struggling to distance themselves from Bush. This allowed Democrats to go with their heart, which ended up leading them to choose Barack Obama.