This is the definitive Jimmy Carter anecdote. Once, when he was president, a bemused journalist asked if it was true that the leader of the free world was in charge of the schedule for the White House tennis court. Of course not, said Carter; don’t be silly. What he had done was tell staff they must speak to his secretary if they wanted to book a tennis session. That way, he elaborated, people cannot use the court simultaneously ‘unless they [are] either on opposite sides of the net or engaged in a doubles contest’.

Honest, wonky and utterly without humour, Carter was probably one of the smartest American presidents and, consequently, one of the worst. Two new accounts of his time in office bring clarity and depth to the record, albeit with varying degrees of sympathy. As Jonathan Alter argues in His Very Best, Carter tends to get studied in relation to something else – economics, piety – and he is one of the first to consider Carter on his own terms. He was ‘disciplined … incorruptible … austere’, determined to do his best, self-punishing when he hadn’t. He was inclined more towards ‘humanity’ than ‘human beings’.

Carter grew up in rural Georgia, served in the navy, trained as an engineer, ran the family peanut business and was elected governor of his home state in 1970. He decided he wanted to be president and, by God, he made it happen. His candidacy in 1976 seemed so improbable that when he told his own mother he was running for president she replied, ‘president of what?’, yet Carter brought his outsider, Christian shtick to the public just when they wanted it the most. Richard Nixon had destroyed the reputation of politics with Watergate. ‘Jimmy Who?’ was a chance to revive it. He fought for the Democratic nomination one handshake at a time, sleeping in spare rooms rather than hotels. He wore a cheap suit and carried his own bags. The summer of 1976, Alter rightly says, was the high point of his political career. He beat the Republican candidate, Gerald Ford, in November, by a narrow margin. After that, things fell apart.

Not immediately though, as Rick Perlstein reminds us. Reaganland is the latest volume in his epic history of the modern American Right, and Carter’s mismanagement of the United States is a necessary part of that story. Although the Democratic establishment and the press were sceptical of the new president in 1977, the public was initially spellbound and rated him highly, even as he did odd things like give them energy-saving tips or put solar panels on the White House roof. Both authors agree that the president was correct in his diagnoses of America’s ills and ahead of his time on some of his cures (Perlstein doesn’t like them all). He wanted to reduce the country’s reliance on Middle East oil and to conserve the environment, as well as to introduce a human rights-based foreign policy. He also sought to balance budgets and confront the Soviet Union: Carter wrote in his diary that he felt more at home with conservatives than liberals, which was increasingly obvious. One of the few Democrats who did get on with him was Senator Joe Biden of Delaware, who, Perlstein notes with distaste, also championed tax cuts and mandatory sentencing. Carter’s unusual blend of commitments went to the heart of the problem: a president elected on his personality had no ideological constituency, and familiarity breeds contempt.

Carter’s annus horribilis was 1979. Perlstein lists all the things that went wrong before the president even did anything: the John Wayne Gacy murders, the Jonestown massacre, petrol supplies running low, revolution in Iran and America’s space station, Skylab, falling out of the sky (and that’s not to mention the nasty bout of haemorrhoids with which Carter began the year). It snowed in California and ‘fifty-two whales simultaneously stranded themselves on a Mexican beach’. Come summer, Carter – now disliked by almost everyone – tried to regain control with a piece of politico-religious theatre: he disappeared to Camp David and returned to deliver an extraordinary speech that both authors commend for its indictment of America’s spiritual malaise. America consumes too much, he said; it has forgotten the principles upon which it was founded.

Again, the voters briefly enjoyed the novelty of a politician blaming them for their own problems and his approval ratings shot up, but then Carter undid all his good work by demanding the resignation of his entire cabinet, which made him look chaotic. His vice president, Walter Mondale, who was thinking of resigning, told a colleague: ‘It went from sugar to shit right there.’ American hostages were seized in Tehran by supporters of Ayatollah Khomeini in the autumn of 1979; the USSR invaded Afghanistan on Christmas Eve. Carter was challenged as the Democratic presidential nominee by Ted Kennedy, and though he won the primaries, by the time he was renominated at the Democratic convention in 1980, he was like a clown car – bits kept falling off him. Alter’s account of his big speech on that occasion is painful to read. With typical masochism, he only gave himself four hours’ sleep the night before. The autocue malfunctioned. He misnamed the liberal icon Hubert Horatio Humphrey as Hubert Horatio Hornblower. The balloons that were supposed to fall got stuck. And when Kennedy appeared on stage with the president, he refused to hold his hand aloft in the traditional display of unity. Carter thought he was drunk.

And yet the Democratic convention gave Carter a poll bounce that put him within a few digits of the Republican nominee, Ronald Reagan, probably because many voters still thought Reagan was a right-wing nut. Alter and Perlstein stress the importance of contingency: Carter was not doomed to defeat; events got out of his control. Perlstein is a little more critical than Alter of the president’s policies because he is himself a liberal. He obviously does not approve of his war on inflation, his spending cuts or his failure to pick a side in the nascent culture war, trying to appease Right and Left so gracelessly that a comedian joked that they would carve Carter’s likeness on Mount Rushmore if they could find room for two faces. Perlstein does make it clear, however, that the Republicans by this point were so agile, well financed and (one might infer) cynical that they had made it nearly impossible for a Democrat to build any kind of consensus around God or patriotism. By the late 1970s, Republicans were already alleging election fraud, comparing rioters to insects, demanding a trade war with Asia and even fretting about disease control. Whereas Alter sees Carter as ground-breaking in a good sense, because he understood that his party had to move to the centre, Perlstein portrays his presidency as ground zero. If you think Trump was unpopular, just look at Carter’s ratings. When a trade unionist was asked what Carter could do to improve his standing, he replied: ‘Die.’

Both books are excellent. Perlstein is the pre-eminent chronicler of America’s conservative turn and my only caveat is that the casual reader might want to read his earlier books first to understand fully what’s going on. Alter has written perhaps the most enjoyable biography of Carter yet, one that might become the standard volume for anyone seeking to understand the president that The Simpsons called, jokingly, ‘history’s greatest monster’.