Emmanuel Macron’s grip on political power seems unshakable after the first round of France’s legislative voting on Sunday. Mr. Macron won the presidency of France in May, a mere 13 months after starting his political movement, a remarkable achievement ratified by Sunday’s vote.

Projections indicate that his party, La République en Marche (The Republic on the Move), may win more than 400 seats in France’s 577-seat National Assembly after a final round of voting on Sunday. That would give Mr. Macron the ability to freely enact promised reforms to jump-start France’s lagging economy and encourage job creation, something his three immediate predecessors tried but failed to do.

Sunday’s election does not, however, reflect enthusiasm on the part of a majority of French voters. More than half stayed away from the polls, the highest rate of voter abstention since 1958. And with the political opposition in tatters, and many political novices owing their seats to the president, Mr. Macron could face temptations to abuse executive power.

Mr. Macron has already moved rapidly to bolster security in the face of the continuing terrorist threat by creating a national counterterrorism center at the Élysée Palace, reporting directly to him. He has also drafted a bill, which will be presented at a cabinet meeting on June 21, that would permanently legalize much of the state of emergency declared by President François Hollande shortly after the terrorist attacks in Paris in November 2015.