(CNN) House Speaker Nancy Pelosi is concerned President Donald Trump will not voluntarily step down unless Democrats win by a "big" enough margin in 2020 that he doesn't contest the results, the New York Times reported Saturday.

In an interview with the newspaper this week, the Democratic leader expressed worry over a scenario where Trump would not accept the election results if he were to lose re-election by a slim margin, the Times reported.

"We have to inoculate against that, we have to be prepared for that," Pelosi told the newspaper Wednesday.

Pelosi told the Times she had worried that Trump would "poison the public mind" and "challenge each of the races" if Democrats didn't win by an overwhelming majority in 2018.

Democrats picked up a net gain of 40 seats in the 2018 midterms — the largest Democratic House gain since 1974.

Read More