President Donald Trump has returned to his Mar-a-Lago resort to find a winter White House that increasingly has become embroiled in the politics of his first year in office.

Mr. Trump will stay at the Palm Beach, Fla., resort through Sunday to celebrate Thanksgiving with his family. The trip marks his first return to the resort since April, after he spent many weekends over the summer at his golf club in Bedminster, N.J.

The...