The White House retaliates, and in short order the Post and Times appear together before the Supreme Court to plead their First Amendment argument for the right to publish the material. Meanwhile, newspapers across the country pick up the story in solidarity with the Post and Times. The court rules 6 -- 3 in the newspapers' favor, vindicating Graham's decision. Nixon demands that the Post should be barred from the White House. One year later, security guard Frank Wills discovers a break-in in progress at the Watergate complex after a guest at the Watergate hotel called complaining about people using flashlights.

Based on this passage, who was president during the movie the post? Let's think fast. Stream of consciousness:
The relevant sentence in the passage is: Nixon demands that the Post should be barred from the White House. So the final answer is Nixon.