The only thing standing between Senate Democrats and an electoral wipeout in 2018? Donald Trump’s base.

A party that’s only three seats short of a Senate majority is nonetheless bracing to play defense for the next two years, hoping to hold a daunting 10 seats in states that went red in last week’s presidential race.

In some of the states — Indiana, Missouri, Montana, North Dakota, West Virginia — Trump’s margin of victory reached nearly 20 points or more. Another five — Michigan*, Pennsylvania, Ohio, Wisconsin, and Florida — unexpectedly swung in the GOP nominee’s favor, instilling fresh fear in Democrats that seats once presumed safe are anything but.

Democrats are nervous not just about the fact that Trump won, but how he did so. The New York real estate mogul won because of his popularity with white working-class voters, whose slow drift from the Democratic Party he accelerated to devastating effect. They abandoned Democrats as few, even seasoned, party operatives suspected they could, leading to victories in places like Michigan and Wisconsin that President Barack Obama won easily just four years ago.

A new game plan

Now, these re-election-seeking Democrats must come up with a game plan to win those voters back — or risk watching their party lose big when they can least afford to see their ranks thinned further.