President Trump on Monday was the latest big political star to swing through Mississippi and boost a candidate in a red-state Senate race that suddenly seems competitive.

© Doug Mills/The New York Times

Former President Barack Obama had cast his successor as out of touch while jabbing at his extravagant sense of style. Mr. Trump responded at length.

© Doug Mills/The New York Times

President Trump will stump for a senator in a state he has won three times by double digits, and as Democrats see a path to victory.

© Haiyun Jiang/The New York Times

Federal law enforcement officials said they were investigating a series of letters mailed to members of Congress and secretaries of state in recent days.

© Tierney L. Cross for The New York Times