Looking at the current American presidential campaign, where one frontrunner is touting his candidacy by trying to convince the electorate that he will rid the country of Mexicans and Mohammedans, you would be forgiven for wondering whether America’s political culture has sunk so low that ramshackle candidates of this sort are the best it can offer. In Barton Swaim’s account of the three years he spent as speechwriter to former South Carolina governor Mark Sanford, readers will find many of their worst suspicions about the tawdry incoherence of American politics confirmed, but they will also be treated to an exceptionally funny jeu d’esprit.

Sanford served as governor from 2003 to 2011. A fiscal conservative and a vociferous critic of President Obama’s bailouts after the 2008 stock-market crash, he is nevertheless best known for going missing for six days in 2009 (neither his wife nor the state police knew where he was). After repeated enquiries, his office eventually claimed that he had gone hiking along the Appalachian Trail. In fact, he had been enjoying a leisurely tryst with his mistress in Buenos Aires. When he returned home, instead of trying to deny the undeniable, Sanford called a hasty press conference and, in a cringe-making, lachrymose confession, admitted to cheating on his wife with a middle-aged Argentinian journalist.

One of the great strengths of The Speechwriter is that, while it is written as a kind of political memoir, it has all of the virtues of good comic fiction: a seamless narrative, a cast of well-drawn, amusing characters (headed by Sanford himself, who comes across as a weirdly parsimonious,