(CNN) As her rivals for the Democratic presidential nomination battled over Medicare for All and the intricacies of federal immigration law during Tuesday's debate, spiritual author Marianne Williamson had a message for them: Wonky won't win.

Time and again on the debate stage, she countered policy talk with sweeping language that cast the 2020 presidential race as a fight between darkness and light.

Her comments get at a larger critique of the Democratic Party she has made before: Plans won't defeat Donald Trump in 2020. She noted in the first debate that Trump didn't win in 2016 by having a plan but by having a message.

"If you think any of this wonkiness is going to deal with this dark psychic force of the collectivized hatred that this president is bringing up in this country, then I'm afraid that the Democrats are going to see some very dark days," Williamson warned during the exchange about water contamination.

Asked about the crisis of contaminated water in Flint, Michigan, she warned of a "dark underbelly of American society." When discussing reparations for the descendants of enslaved Africans, she spoke about the "great injustice" of slavery and the lingering "toxicity" it has left in the lives of Americans.

Read More