PARIS — Even as left-wing supporters were still celebrating the unexpected defeat of France’s far right at the polls, attention turned Monday to the sobering task of how to govern a deeply divided country as it moves into uncharted political territory.

       While an alliance of leftist parties came in first, with more than 180 seats, it is far from the 289 seats needed for a majority in the National Assembly, the powerful lower house of Parliament. President Emmanuel Macron’s centrist Together coalition got more than 160 seats, while the far-right National Rally and its allies were third, winning 143 seats. Polls had predicted that the far right would come in first and perhaps even win an outright majority.