President Jimmy Carter phones Reagan to concede the 4 November 1980 election when there is still bright afternoon sunshine at Reagan's house in California. In actuality, Carter called to concede about 6pm Pacific Time, which would have been dusk at Reagan's house.
In a scene set prior to their 1952 marriage, Ronald and Nancy watch the 1946 Rita Hayworth movie Gilda on TV. At that time, studios were not releasing major hits of recent years to television but were still re-releasing them to theaters using them as second half of double bills.
Ronald Reagan is presented right-handed in the movie. In reality he was left-handed.
Reagan and studio exec are shown walking through picturesque Universal Studios back lot sets late at night, only to enter a door to European building in which he will pose for publicity photos with a chimp for Bedtime for Bonzo. In reality such photos have been shot in photo gallery or sound stage nowhere near back lot and certainly not late at night.
What the movie showed was a walk through a stage set (not back lot) lit AS IF for night. It was not meant that the still shoot was taking place at night.
In the debate between President Carter and Reagan the voice the actor uses is completely wrong. Carter had a very distinctive southern drawl.