CAIRO — Days before Egypt’s presidential election, President Abdel Fattah el-Sisi’s beaming visage adorns billboards across Egypt. His rivals are in jail, the news media is in his pocket and his sole challenger — a politician so obscure many Egyptians would struggle to name him — hasn’t bothered to campaign.

With the Irish bookmaker Paddy Power putting Mr. Sisi’s odds of losing at 1 in 500, most Egypt watchers are already looking past the vote that starts Monday to his next challenge: whether he can change the Constitution to extend his rule beyond the current eight-year limit.

The mystery, then, is why Mr. Sisi is acting like a man with something to lose.

As the election loomed, the Egyptian leader sometimes acted in ways that looked oddly jittery. He fired his army chief in October and a powerful spy chief in January. In speeches, he struck a choleric, sometimes threatening tone, railing against unspecified enemies. In a fierce media crackdown in the final month of campaigning, the government expelled a British reporter without explanation and even imprisoned a pro-Sisi TV host deemed to have stepped out line.

“It’s very confusing,” said Mohamed Anwar el-Sadat, a presidential contender who quit the race in January out of concern for the safety of his campaign workers. “Sisi has everything in hand. So why the fear?”