Dennis Quaid, 70, plays the 40th president—from his 30s (with help from digital de-aging) to his 1987 “Mr. Gorbachev, tear down this wall!” speech to his 80s. Penelope Ann Miller, 60, portrays Nancy Reagan, Lesley-Anne Down, 70, is Margaret Thatcher and Jon Voight, 85, plays a KGB agent who spies on Reagan.