WASHINGTON—Mercedes Schlapp, a White House senior adviser for communications, is taking a new job advising the Trump campaign, the latest administration official to cross over to the re-election effort ahead of the 2020 contest.

Ms. Schlapp, who joined the White House in September 2017, will help the campaign with “strategy as well as Latino outreach with her bilingual capabilities,” Trump campaign manager Brad Parscale said in a tweet. “We are good friends and it’s great to have another die-hard @realDonaldTrump supporter!”

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