In the aftermath of Donald Trump’s 2016 election victory, analysts fiercely debated the role of the approximately six million voters who supported President Barack Obama in 2012 but shifted their support to Mr. Trump in 2016. Democratic strategists also had to worry about their future behavior: Was 2016 a temporary blip or were these voters gone forever? With newly available data from the Cooperative Congressional Election Study survey, the largest publicly-available election survey, we can now analyze what happened with these Obama-Trump voters in 2018 and what that might portend for Mr. Trump’s re-election campaign.

To understand the potential ramifications of Obama-Trump voters in 2020, it’s worth understanding how they voted in 2018. Among those who voted, three-quarters stuck with the Republican Party. But Democrats did win back about one-fifth of the Obama-Trump group in 2018, which would amount to a net swing of about 1.5 million votes. While the idiosyncratic governing style of Mr. Trump may have been one key factor in bringing Obama-Trump voters back into the Democratic fold, it wasn’t the only reason. It’s true that most Obama-Trump voters who stuck with the Republican Party in 2018 strongly approved of the job Mr. Trump was doing as president, but interestingly even half of those who flipped back to the Democratic side at least somewhat approved of Mr. Trump. Democrats won back a significant share of Obama-Trump voters not because those voters disliked Mr. Trump, but in spite of the fact that many actually approved of him.

Instead, these voters appeared to be drawn back toward the Democrats by some of the party’s bread-and butter-issues, and in spite of others. On issues like gun control, health care and the environment, these voters look remarkably like the Democratic Party’s base — those who voted for Obama in 2012, Hillary Clinton in 2016 and a Democratic House candidate in 2018. Eighty-four percent of Obama-Trump voters who voted for Democratic House candidates in 2018 want to ban assault rifles, compared to 92 percent of the Democratic base. By contrast, 57 percent of Obama-Trump voters who stayed with Republicans in 2018 support an assault weapons ban (which has far less support among the Republican base).

Medicare for all is surprisingly popular among all Obama-Trump voters, but especially those who voted for Democrats in 2018. Eighty-three percent of those who switched back to the Democratic Party in 2018 support Medicare for all, nearly as high as the 93 percent support the policy achieves among the most solidly blue Democratic voting bloc.