WASHINGTON (AP) — Former President Barack Obama warned Democrats against being “complacent or smug” about the presidential race at a grassroots fundraiser Tuesday for presumptive Democratic nominee Joe Biden, calling on viewers to learn the lessons from 2016 and not take the election for granted.

But in the era of President Donald Trump, Democrats believe Obama’s appeal, especially among Black and younger voters, can help boost energy for Biden.

They believe the focus on Obama will help reinvigorate Trump’s base, and remind waffling Trump voters — those considering voting for Biden, or staying home — of their dissatisfaction with the prior administration.

Trump campaign deputy communications director Ali Pardo said that together, Obama and Biden “put ‘kids in cages’ and failed to stop China from ripping off Americans while overseeing the worst economic recovery since the Great Depression and stagnant wage growth for American workers.”

Biden’s embrace of Obama during the Democratic primary created some headaches for the former vice president within his own party as well.