This epigraph was added to the novel at the last minute, replacing a quote from the Joni Mitchell song 'Cactus Tree'. It was meant to insinuate President Nixon's guilt in the Watergate scandal.
At the time of the novel's publication, Nixon was facing investigation over whether he was involved in a Republican plot to break into the Democratic party headquarters in the Watergate complex during the 1972 Presidential election, or whether he had organised a cover-up of the crime. By 1973, Nixon was facing increasing pressure, and was forced to dismiss two close aides, H.R. Haldeman and John Erlichman, as well as White House Counsel John Dean.
It became apparent in that year that Nixon had a habit of recording all conversations and meetings at the White House, and these recordings were subpoenaed by the special prosecutor and the Senate. Nixon refused to release them, but by 1974 he was forced to hand them over at the behest of the Supreme Court. One tape clearly revealed Nixon learning of the break-in a few days afterward and discussing means of blocking any investigation. It demonstrated that Nixon had lied in his denial of knowledge prior to March 1973 and denial of political motivations in his instructions to the CIA to falsely claim national security was at risk because of the investigation.
Facing impeachment, President Nixon resigned in August 1974.